Some things that might help: Finish dinner two or three hours before bedtime, skip the alcohol and caffeine, switch off any and all screens the last hour before bed (f.lux and Night Shift mode help, but in the last hour it's still best to stay away entirely), and choose some relaxing activities to do instead. Try coloring, reading a print book, taking a warm bath or shower, doing a face or hair mask, painting your nails, drinking herbal tea and stargazing...whatever makes you cozy. Then actually get in bed at bedtime, and out of bed when your alarm goes off.
If a sudden schedule change feels basically impossible, The National Sleep Foundation suggests small 15-minute adjustments. Usually go to bed at 1 a.m., but wish for an 11 p.m. bedtime? Hit the sack at 12:45 a.m the first two nights, then dial it back to 12:30 a.m. for two more nights, and so on.
(Stressful thoughts keeping you up? Leave your bed for a bit, get comfy somewhere else with low light, and read or like, play solitaire with an actual deck of cards, until you feel sleepy again. Avoid looking at the clock. And if it happens consistently, it could be a sign of anxiety, which is 100% treatable.)