This is what I have done so far
cd /nodebb/node_modules
mkdir nodebb-theme-nameoftheme
git clone https://github.com/NodeBB/nodebb-theme-quickstart.git nodebb-theme-nameoftheme
Edit package.json, plugin.json and theme.json.
In each file replace nodebb-theme-quickstart with nodebb-theme-nameoftheme
In theme.json change the name and description
Activate the theme
Rebuild and Restart
Edit header.tpl to add some text
<title>{browserTitle}TEST123</title>
Save and refresh the page. No change. I am sure I missed some steps. I am documenting how I do this so I can share with the group