I have a few tips that worked for us to get our son to go to sleep in his crib without crying, although we haven't mastered the staying there all night part quite yet.
We are not keen on the leaving to cry (Weisbluth - healthy sleep habits, happy child) or controlled crying (Ferber - solve your child's sleep problems) approach so I won't cover that here but I think it's very easy to find guidance in books such as those in brackets above or online for that if you want to try it.
What helped for us is:
Make sure the child is tired enough to go to sleep. This means have him on an appropriate schedule for his age. At 15 months he's probably about ready for one nap a day if he's not doing that already. If he's had a nap too close to bedtime then he won't fall asleep easily and will get upset when you try to make him.
Start a bedtime routine so he knows what to expect. Dinner, bath and milk is a good start but encourage him to stay awake while he has his milk.
After his milk, do a quiet, enjoyable activity with him in the crib until he gets sleepy. We read a few books and let him hang out with his soft toys. Sometimes we "help the soft toys go to sleep".
Once he seems sleepy ask him to lay down and go to sleep. You can help him by patting or rubbing his back.
Apparently, it is possible to reduce your input gradually, although we haven't got very far with this yet. The theory is, you may start by patting your son to help him sleep, then just having your hand on him, then sitting/standing next to the crib but not touching him and eventually you can leave the room. We sometimes get to the second stage or the third on a good day.
You can try this, I can't promise it will work but we didn't believe it would work for us until we tried it. He may protest to start with but I wouldn't recommend to let him cry a lot (unless you want to use one of the crying methods) or he may start to like his crib even less. But now my son got to know the routine he happily goes into his crib and often lays down by himself after reading his books.
One other thing that helped for us - we got my husband doing the last step of reading the books and putting to bed. My son is quite clingy with me so he would want to be close to me which made it difficult to get him to stay in the crib. After he got used to it though, it's OK for me to put him to bed in the crib. You could also try giving him a favourite soft toy.
If it really doesn't work now, you may find it works better in a month or two. We tried getting our son to sleep in his crib when he was 8 months and it didn't work at all. At 15 months you have the advantage of being able to communicate more and I find my son now loves to know what's happening next, much more than he did when he was smaller (he's now 16 months).