The woes of the day one SteamOS beta. I lived through the pain so you don't have to!
smh. SteamOS beta... Ya know, the instructions were written by an engineer for this beta... Need I say more? After some issues that I had to do some digging to resolve, I got this thing up and running. I braved this so you can wait until it's ready... and that's what I suggest you do! WARNING: There is no third party support for hardware and/or peripherals of any kind beyond the most basic PC components! YMMV based on your configuration!
Here is a video walkthrough I found from PCPer, after I suffered through the process!!!