To get the Artillery Cannon, you first need to obtain the Artillery schematic. The schematic can be purchased for 190 caps from a random vendor - try the Watoga Market vendor in Cranberry Bog. The Artillery schematic can also be obtained for free by progressing in the main story until you are able to bypass the laser fence blocking a room in Fort Defiance. The Artillery schematic can be found on the desk. The Artillery Emplacement works just like it did in Fallout 4. After it is built and placed, connect it to power (requires 3 power). Once the Artillery is hooked up, you can collect extra smoke grenades from the crate. The range on it has been improved, so you can it launch from far greater distances. Throw a smoke grenade into a group of enemies, then wait a few moments for shells to rain down on the enemies. Almost anything will be killed, and you can always restock on grenades from the Artillery crate. Note: The Artillery Cannon is connected to your C.A.M.P. -- so it can be destroyed if you leave and another player destroys it.