The best way to create a checkout to work with thinkific that will allow me to use their functionality

I’m a keap pro user and I’m trying to create a checkout for thinkific. Previously my landing page was on Leadpages but I couldn’t use coupons on there. So I moved my landing page to my own website and would like to create a checkout form that will allow me to collect the customers information. Apparently to use the coupons and affiliates it needs to be the thinkific checkout form, but I don’t believe that form will input the contacts into keap. From what I understand keap pro doesn’t do coupons or affiliates on their own. What might be the solution and has anyone used thinkific before where they solved this issue?
Thanks in advance, Mitch