Biztalk to webMethods

I have a partner that is running Biztalk and trying to send documents to our webMethods system(IS 4.6) over HTTPS, but authenticating with userid/password.

Hi I am facing a similar problem where TIBCO is sending data over https to our webmethods flow. They are very well able to hit the URla nd hit our WM flow using CA certificates. Please suggest how do we capture data received in webmethods flow over https