I would just put it on, guide it to the teat, and just hold it there until you see it really suckling. Some of mine were really clumsy about it at first, as well, and I had to hold them and literally guide the teat into their mouth. Once they start suckling/kneading, though, they are usually stuck on pretty good. If you try and the pup doesn't latch, try a different teat. The pup might not be getting anything from the one he is on.