1. Make sure that you've got the latest version of Pimax firmware and Piplay.
SteamSetup dowload link
2. Install steam then find steamVR.
and install it!
3.Make sure Piplay has been hooked up with pimax mode, then click on the "VR" icon on the upper right of the steam interface to open steamVR.
4.If this is the first time you run SteamVR, you must run the room setup.
AND NOW, you're ready to play steam games with your Pimax 4K!!
Tips: Have you tried playing Warthunder in VR mode, its pretty cooooooooooool!!!!.