I'd try two things - first, let the puppy get used to the colar. put it down, let him sniff it and check it out, so he knows it won't do anything to him. Do this off & on for a day or two. Next, I would get a second person to help- one person can scratch his ears, talk to him, & hold his attention while a second person slips the collar around his neck. (assuming this is a buckling collar & not a choke chain). It just takes a little patience!
*edit* oh- & reward the puppy while his collar is on - give him a little treat, take him out, make it fun. Try putting it off & on a couple times a day (followed by treats) so he associates it with good things happening!