Help needed with payment gateway setup


I recently designed a room rental website from a theme that I purchased. I am about finished with the design and layout, but stuck on the payment process. I am not a programmer and not even sure how I got this far. I am not looking for free help. I just don’t want to make any mistakes connecting the payment gateway(s). I need help with moving forward with finalizing my website and possibly other tasks if your’e willing.

This is the setup that I have right now:
THeme: Bellevue - Hotel + Bed & Breakfast Booking Theme
Booking system: Pinpoint Booking System PRO - Book everything with WordPress