Add TOS to Membership registration

I have a membership site set up and really love how it works except for one issue: I can’t get the terms and conditions that all users MUST agree to to be presented to the user during registration and to prevent them from signing up without agreeing.

The membership plugin uses its own registration form and not the default WordPress multisite one. Does anyone know a way to incorporate some kind of required terms agreement into THIS registration form? Thanks for the help.