Bedtime Routine. Please Help 😫

I have a 3 year old and a 1 year old, I cannot get them on a sleep schedule to save my life. They literally stay up until 1-2:30am every single night, and gets up around 12:30-1pm. I honestly don’t know how they got on this schedule at all. They were going to bed at 8:30pm and getting up at 7-8am every morning. And now I’m completely stuck on the schedule myself. What can I do to get us back on a schedule? Any tips, tricks, or advice would be greatly greatly appreciated!