Additional user info firebase web with a form

I'm using firebaseUI to create a custom CMS where people can log in / sign up and then fulfill fields about themselves (location, company name, account description...)

I'm stuck to the last part when the user is logged in and redirected to a 'welcome page'. I managed to store authentification info in the database with the uid, but I'd like to go further :

On that 'welcome page' I want to display a form that the current user can fill and then store the data in the database in the same place where email address and display name are stored.

My database is built like that : 'users' and then uids with corresponding auth info.

I've been trying to follow the firebase docs but I didn't manage to accomplish that.

Thanks for you help