Lack of documentation on paid memberships

I recently upgraded to an ecommerce plan, but am running into problems setting up a paid membership program.

My goal is to allow a user to come to my site, purchase a membership, then create an account to access a unique page with that content.

If I try to add the default “add to cart” button a template product page, clicking it takes the user to the sign up page instead. Can I not have a user purchase the plan and create their account at the same time like most other ecommerce platforms?

Here is the product page showing what I mean - minimalgoods