Flip the 2.8" PiTFT display over and locate the pad with label #18. We need to cut this trace in order to properly use GPIO 18 (The Y Button is wired to this GPIO). By default, when GPIO 18 is triggered to ground, it will disable the LED backlighting on the display - Cutting the trace here will disable that feature.
Use a hobby knife to mark in between the two pads and make sure it is deep enough to fullly break the trace.
That's pretty much all we need to do to the PiTFT display!