There are several ways to start the playback of an item, the easiest method being to Double-click the item you want to hear. Items that can be previewed are:
Track
Release
Chart
Beatler has a continuous previewing function that will play the next track from the current list automatically after playback of the current track has finished.
Alternatively you can manually build a playlist of items to listen to by Right-clicking on the track and selecting Add To Playlist.