You install Steam, enable proton compatibility (on all games or on RL specifically), download and launch the game. Even more chance that it works on the first try with Arch linux-based distro, since the kernel version is closer to the ones running on the Steam Deck.

If you got the game from the Epic Games store, you download and install Heroic games launcher and proton. In the game settings, you specify the install path of proton and it should be good to go