No need to do anything on your side, just launch it from the SD and play!
The default control scheme:
D-Pad and Left Analog stick is for movment.
A button to interact or confirm.
B is to go back (but not in time).
Y is for opening the menu.
This hint also can be found in-game, so no need to leave this page open.
Unfortunatly, Valve does not allow developers to manually start reviewing process for Deck, and I need to wait until they will select my game for review. But everything is already done, so game is playable on Steam Deck! Just launch it and enjoy.
Have fun!