Depending on how the plates fix to the surrounds, there's a few ways, I've fitted them in the past, ended up only putting a surround on the rear as the moulded plate fixing point on the front bumper was to small for the surrounds I had.
On the rear, I initially used sticky pads to fit the surround then fitted the plate Grrrr over a pot hole ****** thing fell off lol.
So the best way is to fix the surround using a screw fixing kit, worked for me. hope this helps.
Post a link of your purchase, might get a better idea.
Mac