It also took me some time to figure it out, especially the beta was bugged here, but this is the way to do it:
1. Install WSUS 3.0 and abort the wizzard after the installation (= Don't configure anything in WSUS)
2. Install the "ConfigMgr Software Update Point" Role and configure your proxy settings (I assume thats the missing step)
3. Configure Software Update Point Component: "Active software update point on site server" and "Synchronize from Microsoft Update".
Make sure the ports are correct (and select the updates you wish to receive - the product list will be updated after the first sync)
So the highest Software Update Point in the hierarchy needs a local WSUS installation and takes it completly over,
you will notice that the settings in SCCM will be reflected on the WSUS Console...