To start sharing your media with the streaming devices on your network, click the Start button. OnScreen will run in the background until turned off, so once started you can quit the configuration app at any time.
The first time you start OnScreen it will create artwork for all of your shared movies. This process can take some time but you can start using OnScreen right away. Movie artwork will appear on streaming devices as soon as it's available.
From the configuration screen you can control what types of media are shared:
Music: Shares your iTunes music, playlists, and podcasts.
Photos: Shares your iPhoto library, albums, and events.
Movies: Shares movies from iTunes and shared movie folders.
iTunes Movies: Shares all compatible movies from iTunes including podcasts and iTunes U content.
Shared Movie Folders: Shares movies from folders on your computer, external hard drives, or network shares.
To add a folder, click the plus button or use Finder to drag it onto OnScreen's window or dock icon.
To rename a folder, double-click it and type in the desired name. You can view the path to a folder by hovering the mouse over it or show its location in Finder by right-clicking the folder and selecting Reveal in Finder.
To access your shared media files, turn on the device you want to use to play them and look for your computer's name in the media server list.
On a PlayStation 3 you can find your computer under the Videos, Music, or Photo sections of the XMB.
On an Xbox the you can access your computer's shared media by pressing the Guide button, selecting the Media blade, then selecting the type of media you want to play.