How can i add a new weapon to dark rp?

Hello, i want to add turrets to darkRP, like in onslought evolved, the turret spawner, where would i type in the codes to make it work?, or do i just make a new lua file and add it with the rest?

This is what it sais when i try to spawn a turret in dark ro with turretmaker swep from onslought: “weapons/swep_turretmaker/shared.lua:52: attempt to compare number with nil”

Not 100% sure but I think it goes into the darkrp/entities folder. I dunno, something in that general area.

ill try that thanks