I presume this program allows you to view content on your PC/laptop from the Slingbox connected to your TV and home network.
If you want to access that same content away from home, then you have to a) locate your public IP (do you know how to do that?), and b) open and forward the port(s) required by Slingbox so your network traffic at that public IP is redirected to the Slingbox.
Those are the basic elements. You need to indicate what if any of these steps you’ve already taken.