You tap the two pins out (carefully, don't scratch the finish on the receiver) with a punch, align the Sidesaddle, insert the "screws" or bolts that came with it through the pinholes in the receiver, and tighten them up.
You have to remove those two pins to clean the gun anyway, it's no big deal to remove them & replace them with what comes with the Sidesaddle. By "screws", I don't mean you screw anything into the gun that damages or changes anything on it, while gluing the Sidesaddle to it sure would.