Integrate Fist Data merchant Service with my eCommerce (magneto) website

I need someone experienced working with First data PEM files and Magneto eCommerce websites. I need to get the Virtual First Data merchant service to function. The first data technician is telling to my IT person that the Path to PEM file needs to be input into Magneto server. The first data also provided the location where PEM file can be downloaded. In some reason my IT person has difficulty locating this file and integrating website with first data.