How do I create a Register/Login functionality using Flask/SQLalchemy?

I would like to create a very simple register/login/logout functionality for my website. Is there a way to do this with solely using the app.py and html files in my template folder? I have tried to use a forms.py, but it does not seem to be linked properly to be working.

If I can create a simple functionality without importing forms, that would be much appreciated. Thank you for your help!