If you wanna shift your sleep cycle, I've heard the way to do it is in 1 hour increments every 2 days. Work out your natural wake time, and set an alarm for 1 hour earlier than that tomorrow. Then after a couple of days at that time, set the alarm another hour earlier, and so on until your wake time is 8-11am or whatever. Eventually you'll start to get sleepy earlier in the night, and you should find it easier to fall asleep.
Apparently you're also meant to get at least an hour of sunlight as soon as you wake up too - tells your brain and hormones it's wakeup time, and so on the other side of the equation your body's more likely to think it's sleep time earlier in the night. The artificial light in computer monitors triggers the same hormones, so if you cbf going outside just play some bright pc games for an hour when you wake up. Or you can buy light boxes to sit in front of, to the same effect. I went through that process a few years ago and it seemed to work for me. If you're really committed, keeping a sleep journal kinda helps too - mark the approximate times you fall asleep and wake up. Then you'll be able to see if your sleep cycle is shifting properly - you should start falling asleep a little earlier after 4 days or so.
This only really works if you're sleeping alright, just at the wrong times. If for psychological reasons you can't get good sleep at any time, then this mightn't really work.