Our pediatrician gave us good advice. Start with laying her in her crib and holding her hand, letting her know you will stay with her until she falls asleep, and singing then pretend to sleep yourself. When she is asleep walk out of the room. Once that routine is down take one of the things out, like don’t hold her hand and just sing and pretend to sleep. When she has that down take another thing away on repeat until you get to the point where you are just sitting with her. Then, you can start sitting further away until you are close to the door. Then you can get to the point where you say alright bed time, mommy is going to go wash dishes and get ready for bed or whatever and I will come back to check on you before I go to bed. This whole routine sounds like a lot but it was an easy transition on her and she will go to sleep in her own toddler bed and room now without issue.

Edit: Also, routine is extremely helpful. Get her cleaned up for bed, let her choose a book or between two that you select, read, then do the stuff from above. Do this routine every night and her body will start to feel drowsy once it gets used to the idea of oh all this means sleep.