API Testing 5 - HTTP methods GET, POST, PUT, DELETE

This is a companion discussion topic for the original entry at https://docs.katalon.com/katalon-studio/videos/httpmethods.html

Please see my question in below page and provide guidance. I am getting 400 Bad request with “Message”:“No files found in request body.”

Is there a way to use Certificate Authentication to POST transactions ? If so can some one please share info on how to do that.
Thanks in Advance!!