How to save the result of radio button in my database

Hi,

In my registration page I put an radio button to check the user_role

I already added the structure in my registration page.

This is a screenshot of my registration page:

I want to know how to save this value of radio button in my database (user or usermeta table) and check if seller’s reference is valid (I already had a table of seller reference in my database)

Any help will be appreciated and thanks in advance!