Thanks to @a_5mith and @Peter-Zoltan-Keresztes

here is the nginx.conf
user www-data;
worker_processes 1;
pid /run/nginx.pid;

events {
worker_connections 768;
# multi_accept on;
}

http {

##
# Basic Settings
##

sendfile on;
tcp_nopush on;
tcp_nodelay on;
keepalive_timeout 65;
types_hash_max_size 2048;
# server_tokens off;

# server_names_hash_bucket_size 64;
# server_name_in_redirect off;

include /etc/nginx/mime.types;
default_type application/octet-stream;

##
# Logging Settings
##

access_log /var/log/nginx/access.log;
error_log /var/log/nginx/error.log;

##
# Gzip Settings
##

gzip on;
gzip_disable "msie6";

# gzip_vary on;
# gzip_proxied any;
# gzip_comp_level 6;
# gzip_buffers 16 8k;
# gzip_http_version 1.1;
# gzip_types text/plain text/css application/json application/javascript text/xml application/xml application/xml+rss text/javascript;

##
# Virtual Host Configs
##

include /etc/nginx/conf.d/*.conf;
include /etc/nginx/sites-enabled/*;

}

#mail {

# See sample authentication script at:

# http://wiki.nginx.org/ImapAuthenticateWithApachePhpScript

# auth_http localhost/auth.php;

# pop3_capabilities "TOP" "USER";

# imap_capabilities "IMAP4rev1" "UIDPLUS";

server {

listen localhost:110;

protocol pop3;

proxy on;

}

server {

listen localhost:143;

protocol imap;

proxy on;

}

#}

@a_5mith
Did that but not working

I have installed nodebb but can't use domain.com instead of domain.com:4567.Can anyone please help.When i installed installed node bb i used explorehowto.com as base url
This is my config.json
{
"base_url": "http://explorehowto.com",
"port": "4567",
"secret": 'xxxxxxxxx",
"bind_address": "0.0.0.0",
"database": "redis",
"redis": {
"host": "127.0.0.1",
"port": "6379",
"password": "",
"database": "0"
},
"bcrypt_rounds": 12,
"upload_path": "/public/uploads",
"use_port": false,
"relative_path": ""
}

This is what i have inserted in
cd /etc/nginx/sites-available/
sudo nano explorehowto.com

server {
listen 80;

server_name explorehowto.com;

location / {
    proxy_set_header X-Real-IP $remote_addr;
    proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
    proxy_set_header Host $http_host;
    proxy_set_header X-NginX-Proxy true;

    proxy_pass http://127.0.0.1:4567/;
    proxy_redirect off;

    # Socket.IO Support
    proxy_http_version 1.1;
    proxy_set_header Upgrade $http_upgrade;
    proxy_set_header Connection "upgrade";
}

}

But it doesn't run on explorehowto.com but instead running on explorehowto.com:4567

@a_5mith
is this right
git clone -b v0.5.x https://github.com/designcreateplay/NodeBB.git .

Don't mind installed again.
But whenever i am installing it is installing development version and not stable.How to solve it

i have disabled last 5 activated plugins.But still error shows up.
Does my ./nodebb setup is correct what i have above stated

I have installed nodebb and configured correctly.It works for 20 min and then if i installed any plugin or theme it is showing the following error occurs saying"502 badgateway"
These are my configuration
url accessed to use nodebb"http://explorehowto.com:4567"

then in
cd /etc/nginx/sites-available/
sudo nano explorehowto.com
i have inserted the following command
server {
listen 80;

server_name explorehowto.com;

location / {
    proxy_set_header X-Real-IP $remote_addr;
    proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
    proxy_set_header Host $http_host;
    proxy_set_header X-NginX-Proxy true;

    proxy_pass http://191.101.6.63:4567/;
    proxy_redirect off;

    # Socket.IO Support
    proxy_http_version 1.1;
    proxy_set_header Upgrade $http_upgrade;
    proxy_set_header Connection "upgrade";
}

}

server {
server_name www.explorehowto.com;
return 301 $scheme://explorehowto.com$request_uri;
}

I have sucessfully installed nodebb.how to change nodebb's category.
for
example:- domain.com/category
to
category.domain.com
I am not referring to external domain in the category.In simple words i want sub-domain forums.Is it possible

OK PROBLEM SOLVED

@a_5mith
Pal i reached the last stage every thing setup
Presntly i have setup domain on http://explorehowto.com:4567
As you said above i have done all the steps.But a problem with the last step
when i used server block like this
server_name explorehowto.com;

location / {
proxy_set_header X-Real-IP $remote_addr;
proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
proxy_set_header Host $http_host;
proxy_set_header X-NginX-Proxy true;

proxy_pass http://explorehowto.com:4567/;
proxy_redirect off;

# Socket.IO Support
proxy_http_version 1.1;
proxy_set_header Upgrade $http_upgrade;
proxy_set_header Connection "upgrade";

}

then using the following code
sudo ln -s /etc/nginx/sites-available/explorehowto.com /etc/nginx/sites-enabled/
sudo service nginx reload

The result is

root@server:~# cd /etc/nginx/sites-available/
root@server:/etc/nginx/sites-available# sudo nano explorehowto.com
root@server:/etc/nginx/sites-available# sudo ln -s /etc/nginx/sites-available/ex
plorehowto.com /etc/nginx/sites-enabled/
ln: failed to create symbolic link `/etc/nginx/sites-enabled/explorehowto.com':
File exists
root@server:/etc/nginx/sites-available# sudo service nginx reload

• Reloading nginx configuration nginx [fail]
  root@server:/etc/nginx/sites-available#

how to install it

i tried
@a_5mith
sudo apt-get install git nodejs nodejs-legacy npm redis-server imagemagick
then result is
-bash: sudo: command not found
so tried
sudo apt-get update
again result is
-bash: sudo: command not found

@a_5mith also but how it worked yesterday on ubuntu 12.04.All installed correctly

@a_5mith Can nodebb and node js support
ubuntu 14.04 x86 minimal

another error
root@server:~# sudo apt-get install git nodejs nodejs-legacy npm redis-server im
agemagick
Reading package lists... Done
Building dependency tree... Done
E: Unable to locate package nodejs-legacy

This is the error i got
Reading package lists... Done
Building dependency tree... Done
Package imagemagick is not available, but is referred to by another package.
This may mean that the package is missing, has been obsoleted, or
is only available from another source

E: Unable to locate package git
E: Unable to locate package nodejs
E: Unable to locate package nodejs-legacy
E: Unable to locate package npm
E: Unable to locate package redis-server
E: Package 'imagemagick' has no installation candidate
root@server:~#

I am doing a fresh install of vps do i need any additional thing to install.Do i need to install node.js or this code have already node js installation
$ sudo apt-get install git nodejs nodejs-legacy npm redis-server imagemagick

I am not getting any reply so i made new one.Pal please help just see the above code.Do i making any mistake

In a new vps with ubuntu 12.04 the following are the codes i used to run installation
sudo apt-get update
sudo apt-get install nano
sudo apt-get install git-core
apt-get install python-software-properties
apt-add-repository ppa:chris-lea/node.js
apt-get update
apt-get install nodejs
sudo add-apt-repository -y ppa:rwky/redis
sudo apt-get update && sudo apt-get install -y redis-server
sudo apt-get install build-essential imagemagick
mkdir mynodebb
git clone git://github.com/designcreateplay/NodeBB.git mynodebb
cd mynodebb
npm install
node app --setup
for the installation url i used
http://191.101.6.63:4567

I didnt found any error in installation
but when i am going to my nodebb page .I am getting"No webpage available"