Bows spawn WITH ammo, you should have 1 shot in your weapon when you spawn it, also this is a thread about tutorials you should probably post this question in a thread.
go to the narc arrow or tranq arrow I forget the name, but the stone toripidity arrow is the weapon arrow, make a child of the narc/tranq arrow and move everything into your own mod folder. update your weapons damage to your own new files. reassign your own ammo files to the weapon and change the weapon templates.