You could listen to relaxation videos or search "relaxation videos" on youtube. After that, listen to them and this could help. I like to listen to whisper videos before I go to sleep. Sorry I know it's weird listening to people whispering but it helps me relax. Try breathing techniques such as breathing slowly, this may help you relax as well. What else you could do is drink milk, read a boring book. You could listen to calming music. When you're trying to sleep, try to think of something in your head calming which could be your favourite place to visit or a beach e.g. You could try thinking an action e.g. walking down stairs, and thinking of it again and again.

I hope this helps you