Register user only when a payment is received

The documentation for the add on (http://www.gravityhelp.com/documentation/page/User_Registration_Add-On) states

"Register user only when a payment is received.
When this option is enabled, the user will not be registered until the PayPal payment has been received."

I don't see an option anywhere that seems to do this? Is there really a checkbox somewhere?

I have created my product form and the corresponding GF PayPal AddOn form (subscription). I have created my user registration form and the corresponding GF Registration AddOn form, but I don't see any way to tie everything together.

Maybe I'm misunderstanding the intended GF flow. Ideally, I would like the user to subscribe via the PayPal form and then when the IPN comes back have the user account created or enabled. Honestly, given the asynchronous nature of the IPN, I'm not clear how the Registration form would ever be invoked.

Any help would be massively appreciated. I'm sure I'm just not connecting the dots. Thanks!

Ah - and the light bulb goes off. There isn't an "option" to enable this. For anyone else that's confused, here's what I did...

1. Created my GF Form
2. Created my PayPal form based on the GF Form
3. Created my User Registration form based off the same GF Form

When the user purchases something via my PayPal form, it is also filling out the User Registration form. In other words, the GF Form I created is being used as the PayPal form and the User Registration form.

I haven't tested further to see if the user account isn't enabled untile the IPN is received, but at least now I see how the elements are tied together. I hope this helps someone else.