API integration with our Financial Partner

I need to integrate my CRM with a 3rd party financial company to be able to do soft credit pulls, hard pulls, upload documents, send documents, all from my CRM. 

I can make a web hook and hit their endpoint fine, but I cannot see a response. I am using JSON to POST. I have no clue how to use a server to do this outside of Quickbase which is the only answers I have been able to find after 5 hours of googling. 

Please help, if you need anymore information from me to be able to assist me I am more than welcome to share, almost anything.