Get first (download):
This great program from JSCones:
http://www.users.on.net/~jscones/software/products-jsgme.html
Put it in C:\Program Files\Ubisoft\SilentHunterIII (if your path is the same).
Make a folder called: MODS ...
Install the above JSGME mod enabler, it will say MODS upon installing and click OK.
Drag your DBSM mod in folder MODS.
Start JSGME and you will see DBSM >> install it to the right side.
Done.
This is how you install all mods, but be aware ... only install mods when you are in base. Sound mods can be installed (I think) always ... even (saved game) on patrol.