Step 1: To start playing CS:GO, you want to make sure you have the beta version of CS:GO downloaded and selected in your Steam Library. In your steam library, right click Counter Strike 2 > Properties > Beta > Select csgo_legacy

Step 2: After having downloaded and selected CS:GO in your steam app, you will now have to change your game version in the INUI application as well. Click the CS logo to go to CS Matchmaking and press the settings button next to "Game version", now simply select CS:GO and hit save.

Step 3: You are now ready to queue into CS:GO matchmaking! Press Play, select the maps you would like to play and hit that Start button! Have fun!