Try this on for size:
on the main screen, open the database.
from there, open the weapon tab.
on the side, where it lists the weapons, there is a button at the bottom that says, "Array Size"
click that button, then there will be a number inside a text feild with two arrows next to it, one up, and one down.
click the up arrow once in order to add another empty slot.
click ok on the little window
click apply on the database menu and Viola!.
Now, once those steps are completed, you can completely create your own weapon using different attributes, animations, ECT.