How to use Membership with this plugin

My goal is to collect additional information when people register for a membership level, such as phone number, business name, facebook page URL, second contact name, second contact email, etc.

The following plugin "Simplr User Registration Form" allows admin to build different/separate registration forms with different custom fields and role. I only need the custom field feature. The role of a paid membership is always subscriber.


Free version

Paid version

Custom fields:

The paid version even has the font end profile page:

My question is: How to use this plugin with the membership plugin? So people can provide additional profile (custom fileds) information during the membership signup process.