I just took that formed piece out of the Garmin with tweezers and placed it equally level. This part is the extension that is under the thin rubber button and this extension depresses the switch below. Once I placed it evenly I formed a dab of liquid electrical tape over it and let it dry overnight. Liquid electrical tape (mine is marketed by "Starbrite") is very durable, highly adhesive and will stay flexible in all types of weather. Once it's dry it should last longer than the original button, by far.
Note, my unit is passed warranty.