@sharonyue to remove the panel you have to edit the template.
I do not know exactly where it is but it should something with topic template.
I am new to NodeBB so during the installation process I hace heard of MongoDB. What is that, where is that stored? I have a SQL database (username of database, database name, host and password) will my SQL database work during the installation process / how do I use it?
MongoDB is a NoSQL database. It's a non-relational database of keys-values objects.
NodeBB doesn't use SQL, so you will not use your SQL database to make NodeBB work.