Registration form redirects to registration form after payment

I'm testing the registration of my Membership Site (one payment for 20 weeks of dripped content) with Paypal Sandbox. Here's what happens:
1. User lands on registration page.
2. There is only one subscription to select
3. User selects that subscription and clicks "Sign Up" (seems a bit redundant)
4. The next page asks user to confirm the subscription. User clicks "Subscribe" and is sent to Paypal to pay.
5. After paying at PayPal, user clicks link to return to site.
6. User lands on the same subscription page as #1.

Besides the fact that the user can't access any content, they can't enter any membership information into an account. It seems to me that they should do it in this order:
1. User signs up as Member
2. User selects Subscription & pays
3. User accesses the member area of the website

I searched the forum & couldn't find any instructions on setting up a "sign up for membership" page, or the return url to give to Paypal. Can someone point me in the right direction?