This adapter presses in to the Bambu Lab rubber foot to keep it from easily falling out of the hole in the bottom of the printer. I use it with the official feet from Bambu Lab on mine however, I'm sure the 3D Printed versions would work the same. Just push the adapters in to the center of the feet and then press the adapter in to the holes on the bottom of the printer. This prevents the feet from just dropping out of the printer when trying to move it around.
Be sure that you push the rubber feet up in to the hole as much as you can as well. There should be about a 1mm or 2 space to push some of the actual rubber in similar to how the official bambu lab install video shows them tucking the rubber in.