Confused about taking orders

Hello everyone, 

I’m very, very confused as to how to proceed with my website. Allow me to explain:

I’ve purchase a one year subscription with Squarespace, basic commerce. As part of setting up, I was told that I needed to set up my payments with Stripe since I want customers to use credit cards. 
So I purchased my domain and associated Stripe with said domain. Both Squarespace provide options for payments… so what am I supposed to do? 
Basically, I want customers to enter their banking information in their own accounts. Once that’s done, I want to be able to bill them every time they use my services (charge their credit cards). I have no idea how to do this however and I’m getting frustrated as I can’t get started until I’ve solved the payment issue. 
Can someone explain how should I proceed please? If possible, as simple as possible.

Thank you!