Installation using DAModder is highly recommended, since it allows for easy installation and uninstallation of the mod, as well as other advanced features.
DAModder: http://dragonagemodding.wordpress.com/damodder

1. Run DAModder and drag and drop the downloaded ZIP file onto the DAModder window.

If you do not wish to use DAModder, this mod can be installed with Bioware's DAUpdater program as follows:

1. Use DAUpdater.exe (located in your Dragon Age install directory, in the bin_ship subdirectory) and select the DAZip file.
2. Select the AddIn in the list and click install.
3. Once the progress says "Installed.", exit DAUpdater and run the game.