I'm so helpful about these 380s eh Whisper
Assuming you have the standard wheels ( big wheel & one straight length of box section stainless as a leg ? ) - there are two threaded holes - one obvious for using the wheels as wheels - the other for when you flip them up . ( just seen pic - yep that's them ! )
Screw them in the bottom hole ( now at the top of the transom) and rest the top ( now the bottom) of the box section against the outside of the transom pad - tighten up the screws and go boating !