Be sure to set up your Oculus Rift and download and install the 1.3 sdk.

Refer to this pofficial steam guide for inital set up : https://support.steampowered.com/kb_article.php?ref=3180-UPHK-0900&l=english

Make sure you set your oculus store settings to be able to run unsupported games.

Launch the game through Steam VR interface. (Top right VR icon in steam.)

When the game starts, you will need to reposition yourself to your seated position. Pressing "back" on the controller will reset the headset to your current direction.

Use head tracking to select menu items and the A button to select.

If you experiences problems with your position in game press "back" to reset.

If the game fails to start, put on the headset and try loading again. On some occasions you may have to do this 2 or 3 times even upto 10 times in some cases. This is down to the oculus SDK.

If the game disconnects, be sure you are connected to the internet.