hello guys, anybody know how add backend and user registration? I finish my webapp works , but there is no backend, 
Go to the firebase console (this is a separate site outside of studio). Here you can enable Authentication using whatever method you like (I would start just with Google Authentication).
This will enable you to get users authenticated into the app.
Create a login screen to prompt for login details and remember to add a logout button somewhere in your app.
To properly store users profiles and allow management of it then probably you also need to add a firestore database (again you do that in console, ask Gemini in console to help if you need). After authentication you need to write that users details to a new document in a “users” collection that you can create in Firestore.
I hope that gives you some quick pointers in the right direction.
Carey
thanks, I will check also youtube for this,