If youre the schedule and routine type of mom

When did you start getting your kids on a schedule I have a 5 year old and a 4 week old. My 5 year old has a bed time routine and in bed between 9/10. When is a good age to start with my 4 week old? I know shes pretty much still on demand at this point but I cannot remember for the life of me when my oldest got into a good routine. I’ve been doing bath time between 6 and 7. Then a bottle at 8. Sometimes she’s asleep by 9:30 sometimes (like tonight) she cat naps on and off until 11 or 12 then will go to sleep for “the night” is really like het in bed by 7 or 8 so I can spend some time with my oldest before bed. Right now my husband is putting her to bed while I’m working on getting baby to bed. So I just keep being consistent with babies routine and eventually she’ll get it? Do I just let her do her own thing and wait longer before I try to get her into a routine? She sleeps decent at night she just has her long sleep stretches at the wrong time lol would love some pointers.