Infusion/Keap soft Api

Hello I am confused on how infusion soft api works. I created a developer account on infusionsoft and created a sandbox infusion soft/keap account and i am able to call infusion soft api to create contacts etc. How would I handle a keap account integration without it being a sandbox infusionsoft account?
Also how do I signup for a keap account I see no option to do so.
Thank you