Getting into a routine?

For those of you that have morning, nap, and/or night time routines and schedules with your babies, how do you do it and actually stick with it? I’ve never had a routine or a set wake up/bed time in my life but I am trying to change that and get my baby and I on a schedule but it’s so hard to stick with it. some nights she goes to bed at 8 pm and some nights she’s up until 4 am. she just feeds when she’s hungry and never at a set time and just naps whenever she wants