The trick is to have an allen key in either end of the reg, i believe off the top of my head they are 3/8 (top) and 5/16 (bottom)
Then depending on which end you want to remove - in your case the bottom cap - hold the allen key which is in the opposite end, and the entire body of the reg steady in one hand, and turn the other key.
I do stress that unless you are experiencing a direct problem with the regulator itself that you leave it well alone, they are built to last, and you seldom need to open them up.
Hope this helps
Ash
Tech department
DYE Europe