You can see the current playlist by clicking/touching the album cover on the lower right. And jump songs from there. Another touch to the cover will zoom in on the cover image, and third touch will take you to the song position screen where you can seek thru the current playing track.

So, to add whole album to the playlist and switch to the fourth track, click on the CD+ button, click the lower-right album image, click the fourth song.

(trev: maybe we should switch to the "Now Playing" screen if the album was added to an empty playlist)