I've placed it in the header between <script> tags and it works great. Thanks for your reply.

I'm using the nodebb-plugin-session-sharing plugin, so that when I'm logged in to my website I'm automatically logged in into NodeBB. In addition I don't need any other ways of loggin in. I've turned off local login, but now the login page is still there but it's empty.

I would like to add a hook and some custom code that redirects me to the login page of my website when I click the Login button in NodeBB. What hook do I need to use? And how do I redirect to an external url?