Hey everyone!
Steam Multiplayer now works in the beta version of v6! In order to access this, you and any other person that wants to play needs to go Properties > Betas > MPTest.
The person that wants to host goes Main Menu > Multiplayer > Host Game
To join just go Main Menu > Multiplayer > Shift + Tab > Join Game
V6 of the game comes out on the end of September
Thanks everyone!
Shanaz