Purchase the game if you haven't already and let it install.

Open the game for the first time through steam.

Realise it isn't that big of a deal to have to download another games client you're not even going to use. C'mon, does it really matter? It's not even a gigabyte and so what if you need another account? If this is a game you want to play then this is the only way.

Start playing the game.

Don't use Linux