- Install the app and open it.
- Enable "Mirror Status:" and enable "QuickSettings Mirror:"
- Either open the chromecast app, and find mirroring in the left panel, or
- Pull down into your quick settings and see the icon for "cast screen"
There is a small bit of lag, which would mean some games that require split second timing would be hard to play on the big screen, but others work fine, like FIFA 14 for example. Any video site (that doesn't already support Chromecast) will work perfectly as well.