Sleep training- keeping baby awake in day? How?

OurJellybean

I've been doing a lot of research on getting babe to change her sleep schedule but I have one question that I can't seem to find the answer to. All the books say to wake lo up at the same time every morning... But does that apply even if they didn't sleep all night? Like if lo was up from 7 pm- 7 am, which she is, do I let us both sleep or torture myself and consistently wake her at say 9 am. I also read to wake them every 3 hours during the day for feeds but after you wake and feed them do you just let them go back to sleep if they want? Or force them to stay awake? I hope this works cuz it sounds hard lol, exsp after being up all night