To feed it from a DC source, leave off the input connector, fuse, transformer, bridge, and 680uF cap.
If you have a regulated 5V source, also leave off regulator. Feed 5V to the regulator pin closest to the fuse, and ground to the middle pin of the regulator.
If you have a regulated or unregulated DC source between 7 and 15V, feed it to the two terminals of the bridge rectifier labeled + and -. You may want to add a 100nF or 330nF cap in place of the 680uF one to reduce the chance of the regulator oscillating.
/mike