Connect my Website to a WebApp using - SOAP APi

Hello, We have a website and we need to connect to the WebApp of our Partner's website using SOAP APi. On our website, we are selling Subscription Plans of our Partner's Website. On the website of our Partner there are 4 subscription Plans ; ( 1 Free Package + 3 other paying Packages ) We only want to connect to the " Free Package " using the SOAP APi " Connect to the Free Package ", means : - Registration process to the WebAPP. - Login Process to the WebApp. You have to be 100% familiar with the - SOAP APi - if you bid on the Project. Very detailed Documentations with graphics are available to help you with the connexion to the WebApp. Best of regards