I'm sure it's a simple process but I don't have the board anymore so I can't experiment. As you may know I recently sold my DS board to a fellow on Shmups (ckong) and I'm asking in order to help him. I only owned the board for a week and didn't configure anything so I have no knowledge of how to access it.
Power up the board, and let it go at least until the copyright screen. Then press and hold the button circled in YELLOW in this pic for a few seconds until you enter the test menu (this is the same for every SH3 PCB):
(http://i147.photobucket.com/albums/r283/blueskied/SH3pcbtestmenubutton.jpg)
You can access all the dip switches via the test menu (adjust screen, ranking, freeplay on/off, extends, extra lives, etc).