The Media Library is designed to display your Media Library items and clips the highlighted item consists of. To add a clip to your current project just drag it to the Workspace. In the left part of the Media Library all of the items are listed, and in the right part you can find the clips displayed according to the selected view.

You can preview the video clips in your Media Library item before you add them to the Storyboard. To do that you need to double-click the desired clip or right-click it and select Preview Clip. The contents of the clip will be displayed in the Preview main window.