[Membership 2] Custom fields on registration form

I need assistance with understanding how to add a customize field to the registration form for Membership 2 Pro.

I’m setting up a membership portal where the current members have membership numbers that I would like to have displayed on their account page.

Plus I need to import the list which has the membership number into the plugin, but didn’t want to do it until I’ve created a place to store that information. Can you help me with that?