Video Tutorial
This video is based on a slightly older version of Subsurface, but should still be very useful to get an idea of the functionality.
You can also download the video for offline viewing, using one of the following links:
http://archive.org/download/Subsurface_v4_Tutorial/subsurface_v4_tut_1080p_2500kbps.mp4
http://archive.org/download/Subsurface_v4_Tutorial/subsurface_v4_tut_720p_1500kbps.webm
… or any other of the links at https://archive.org/details/Subsurface_v4_Tutorial
… and watch it with any video player (e.g.: VLC).