T.F.
What I did with my son was to create a bedtime routine. He has his bath, then we sit together with his comfort things, (in his case his blankie, a sippy of water, and a stuffed animal) and we read a couple stories, and/or sing a couple songs. Then he gives us night-night kisses and it's time for bed. By that time he knows that it's time to go to sleep. At first he had a little trouble getting into the habit, but now, he likes his routine and it seems to comfort him. The routine gives him time to get used to the idea that it's time to sleep. You don't have to do what we do, but I would recommend some routine. Children are more comfortable if they know what to expect. I hope this helps.
T. F.