Start with naps then move your way up. Start a bedtime ritual and nap ritual that you can stick with.
For example... before naptime, I cuddle my daughter for a while to get her to calm down from playing. We read a book and I sing her a song, then she goes down to bed.
After you get that mastered, start working on getting him to sleep in his own bed overnight. For bedtime, we start with a bath, then we brush her teeth, read her "Goodnight Moon" and sing her "Hush Little Baby," then it's time to kiss her goodnight.
There will be drama... afterall he's used to sleeping with you. Kiddos start developing sleep habits before they're 6 months old. When he cries in his crib, let him fuss for a few minutes before going in. Now if he's full-on screaming, go ahead and comfort him. Try your best NOT get pick him up out of bed, and try your best not to talk to him. Just let him lay in his bed and gently rub his little tummy or back to get him to calm down. If you need to you can softly sing a lullaby. As he calms down, remove your hand from the crib, and just stand there for a minute or two. If he starts fussing again, rub his back/tummy to reassure him. Then wait... and once he's finally calm and sleepy, quietly leave the room.
I keep her on a schedule as best as I can. Naps at the same time every day and always to bed for the night on time. The most important thing is consistency. Don't give up. It's going to be a hard habit to break, but you can do it. Find a routine that works for you and stick to it.
Good luck!