Couple of questions. What X-Wing model are you building, AMT, ProShop, SS?
All X-Wing model kits come with the four laser canons. Did your kit not have them? If not, you could make them from various sizes of plastic, aluminum or brass tubing with some greeblie details added from plastic bits or parts from other models you may have laying around. Study pictures of the canons and see what needs to be done.