Er, screw it on? It's a CW thread on a G&P so bear that in mind. It's not a quick detach suppressor so you will need to remove the flash hider first then screw it on.
Edit
It's a bit unique in that you can use it with a tracer unit. As such, the cap comes off (the threaded cap) so make sure that's on there first so that you can actually screw the barrel into something.