carefully remove all the screws and then lightly tap on the side of the grip with a mallet (or something that will not damage the finish or dent it) until the sideplate comes off.
Never pry it off or pound it back on.
Once the screws are out: hold the gun in the left hand with the plate UP, and use a plastic screwdriver handle to rap downward on the frame under the grip area. The plate will pop up.