Your video card software should have basic functions for that. For AMD it's Eyefinity.
Though there are 3rd party programs out there that make multi-screens easier to use.
I've always used UltraMon.
But you can't have 2 fullscreened applications. I don't know how it works, or why it does this, but when you click outside of the fullscreened window, it minimizes. I use to run dual screens when playing games. I'd have the game on one monitor and a browser on the other, but when i click on the browser the game minimizes.