Routine.???

My baby is 18 months I’ve never made her a routine which I regret because she sleeps at 9 and wakes up at 1 am n then sleeps at 4am n doesn’t wake up until 1pm which sucks bc I have to stay up with her until 4 am... any tips or suggestion.?? I want to make her a routine but idk what to do. I don’t work or anything so I’m home all day with her. Thanks

Update: this little girl used to sleep through the night until like a month ago is when she started doing that 😭