Step One: Find your desired game, whether it be from Gamejolt, Itch, or anywhere else. You'll want to download the game anywhere on your computer

Step Two: Find the game, it will typically be in either "zip" or "rar" format. Right click and press extract to somewhere you can easily get to.

 Step Three: Open Steam and navigate to your library, select "add a non-steam game" and press "Browse". From here, find your game and add the "exe" to steam.

 Step Four: Now that your game is on steam, click on the gear icon and select "Properties". Now select "Compatability" and press "Force". Make sure you select "Proton Experimental"

 Step Five: Press Play!