By connecting the external IR receiver to the adapter box, and then plugging the resulting combination into a USB port, you've created an unsightly way to talk to your PS3 via infrared.
In brief, the physical installation simply involved plugging the AV cables (included) into the SlingBox and our set-top box (a Philips Freeview box, to be precise), then taping a couple of IR emitters onto the front of our set-top box, and finally hooking the SlingBox up to our router (via a couple of SlingLink ethernet wall-plug bridges as our router was too far away).