The first step is to back off the roller in the front of the adapter. Use the provided Allen wrench and insert it into the small hole in the magwell and back off the internal set screw. Everything is captured so you don't have to worry about going too far.
Insert the adapter into the bottom of your lower while you press the magazine catch. The adapter should slide in smoothly with a very close fit. The outside dimensions of the adapter are machined to match the profile of a Mil-Spec magwell.
The top of the adapter should be flush with top of the receiver. Tighten down the set screw with the allen wrench. You cannot damage your receiver. You want to use no more torque than it takes to permanently warp the Allen wrench.
3/32 Hex End Key Allen wrench.
