Am creating a custom plugin to have a custom list of 'gyms', to work with Rainlab/User.

Created a migration to modify the users table to have a new column 'gym_id'. In my custom plugin when I create a gym, i am able to list the users with check boxes using the relationship field. But when i check one, save & refresh, it does NOT save the gym id to the users table.

Also how can i add a new field to the Users' update page? I'm trying not to touch the Rainlab/User plugin if possible in cause of updates etc.