L.C.
Swaddling is a good idea and put him down awake or sleepy but not asleep. He will get used to the idea of going to sleep by himself. My son is 8 months and still cries when i put him down for a nap or bedtime, but its only for 30 seconds or so, just to tell me he doesnt like it, but then he falls asleep or watches his mobile until he falls asleep. If he cries longer than 10 minutes, i would pick him up or comfort him in his crib, then try again. Try a mobile or something like that also. It may distract him until he falls asleep.