How can I add members' "FULL NAME" as required when they register.

Instead of full name you can just add first and last name which is basically the same thing. Those are existing WordPress User fields, and you go to the REgistration Fields Options page and got to the middle section and ctrl click on First Name and Last Name and then those fields will be required for when new people register. Hope that helps!

I’m sorry, that was wrong, go to the second section of the Registration Fields page, where the title is “Add Additional Fields to Registration Form” and the while holding down the Ctrl key left click the mouse on First Name and Last Name and that will select those two fields which will then be required on the registration form for new users registering.