Once you add the game to your steam library all you do is open big picture, go to controller settings. You can map the key press to a button on the controller. I have done this myself its the only way I play a Kingdom for Keflings because i don't like mouse and keyboard! it is literally a three step processes so it is kind of magic. If you would like help my steam name is the same as my itch.io name you can add me and I would gladly walk you through it. have a great day! ;)
this process works with all games and almost any controller!
keep up the good work ninja bee we all love you