You can stream an album by going to your purchases page and locating the album, then clicking on the play button beside the track you want to listen. After the track has finished playing, playback will move to the next track in the list until the entire album is played.
Your browser must have support for HTML5 audio and the MP3 format for album streaming to work.
Please note there is currently a bug where newly revealed albums will not play tracks consecutively. Refresh the page to fix this.