Get File Path from a Shell Context Menu

I am struggling with where to start on a new project.  My goal essentially, is to be able to right click one or multiple files within a system, and select an option to encrypt them with 7-zip.  I have a handle on how to do all of it except one part of the logic:  How would I pass the file path to the selected file into the script when I right click it?  Is there a UDF or function I should be looking at?  Any advice on where to start looking would be very much appreciated.  

Kind Regards