We're sorry, but the Steam version of the game is not supported on Mac. However, if you bought the DLCs on Steam, you can move them over to the Mac version of the game downloaded for free here on itch.io! If you go into the folder containing the game by right clicking on the game and going to "Browse Local Files", you should find the DLCs in the "game" folder. They should end with ".rpa". You can copy those rpa files out of the Steam version, into the "game" folder of the itch.io version, and that should unlock the DLCs for you. If you need more help, just let me know!