Step 1 - Remove the retaining plate
The first thing that you need to do is remove the screw that is holding the retaining plate in place. It is removed using a TX-XX drive. Make sure to not lose the screw!
Step 2 - Remove the old gauge
Gently pull the retaining plate away from the domino joiner until you can remove the manufacturer's gauge. Don't use excessive force if it gets caught. It is a thin piece of metal and you can bend it easily! There is a hooking mechanism which can sometimes be stubborn. Be gentle with it, and it will come loose and allow you to remove the original gauge.
Step 3 - Install the new gauge
Slide in the new gauge where you just removed the old one from. (It's that easy!)
Step 4 - Install the retaining plate
The last step is to secure the retaining plate and gauge with the screw that you removed in step 1. After you've secured the gauge, try to sliding the new gauge back and forth. It should be easy to slide back and forth. You should feel the detent catch on all of the positions. If it is too hard, you may want to slightly loosen the screw.