Hey A.,
Our Pediatrician got us on schedule when our baby was 4 months old and I am so grateful! Here's what we did with both of our kids. Bedtime is between 6pm - 6:30pm. After their evening feeding you go through a bedtime routine, bath, story, song or prayers, then put the baby in his crib awake and leave the room. He'll cry but if he doesn't stop after 5 minutes go give him a quick pet, whisper sweet nothings then leave. If he still cries wait 10 minutes this time before you go in. Then 15, etc.
You'll need to adjust those daytime naps too. Try to push him a little longer in the AM (by 30-60 min), and then push the afternoon one a little later and let it last longer. So if he wakes up at 7am try to wait until 9am for the morning nap. Let's say he sleeps until 10:30am. So the afternoon nap could be from 1pm - 2:30pm. He'll be nice and ready for bed at 6pm.
Kids who are well rested are so much easier to live with. And your job is to provide them structure. You need to be as vigilant about their sleep as you are about safety and nutrition.
Good luck and have fun with your baby!