You would type /gimme or !gimmie then the number of the item you want.
!gimme 220
Would give you the Shortstop, for example.
If you look at the Donate page, you should see more detailed instructions on the plugin they used, as well as a weapon index list. I'd post some direct links but this forum account is new and I'm unable to do that yet. Regardless, it's the /gimmie command then the weapon number from that page.