save in user id data

I have on the first screen the login of the users, when they register or enter their data send to screen 2.

I want that when the user enters a value in the textbox, it will be saved in firebase together with the user, that is, if the user luis entered 20,15,14, it will be saved in the user luis.

If the user entered Romeo 14,2,20 it is saved in Romeo. so that every login you can see that result.

I just want to know how to link them to the registration id of each user. Thank you very much for reading