Prompt for Payment Once Form is Completed

[HWJ-Group]

My product I am selling to customers is the digital deliverable I generate once they fill out a form with all sorts of information I am requesting. The challenge I have is how do I seamlessly have a payment button at the end so once they have filled out the form they need to pay the $40 before it sends me their responses? 

I have a great form built with the steps etc., and I also configured a product that they can add to the cart, but the two need to be more seamlessly connected so that all the customer has to do is fill the form out and when they get to that last step it ask for them to pay $40. 

Thank you in advance for your help in how we can solve this. 

Scott

[krooapparel]

I would like to know how to make a form that prompts a payment at the end as well.