The answer to this question is 'what you want is not possible in Windows 8 RTM'.
Using Windows 8 RTM, it is not possible to use two Apps side by side with this exception:
Two apps can be launched if one of the apps is in Metro-Snap mode. You can see this by opening a metro app, dragging the app by its top border to the left or right side of the screen. After this is snapped (we call this metro-snapped), you can hit the lower-left hotcorner on the monitor, open the start screen again (or just press Control+Escape). you now see the start screen, and you can launch another metro app. After this you will have two apps, one snapped small, and one snapped large.
We recently released RetroUI Pro v3 (RetroUI.com), which users the ability to run Apps in resizable windows. We have also integrated support for running multiple monitors using Windows 8. So you can run apps and move them between monitors in resizable windows. With that said, what this user has requested is not possible due to the architecture of Windows 8 RTM.
In RetroUI Pro v3, we released new technology called SuperSize, which allows a Metro app to be spanned across an array which is made up of of multiple-monitors.
Not attempting to hijack this topic, but thought I would shed a bit of light on the topic because I think we understand it pretty well.
To view a demonstration of our SuperSize technology: https://www.youtube.com/watch?v=ldaycb3RUOI
Technical information on SuperSize (Whitepaper)