Support Forum

I might have set up Simple Press incorrectly. (I thought I posted something about this yesterday, but don't see the post today, so excuse me if I am asking this question twice!)

Here is what I would like-

ONE sign-up form with checkboxes,

So that I can use one database for people either 1. Signing-up for my Simple Press forum, 2. Subscribing to my newsletter, via Mailchimp, 3. Signing up for a course I am offering. 

So the form would show (for instance) Sign up for our Simple Press forum and if you like also check the boxes for signing up for our NL and our course offering. 

So one set of login details can be used by each person. 

I use aMember and Mailchimp already, but don't know how to get all three potential sign-ups going to the same database.