Bbt help

This is my first time charting this, I read you just take it before you get up in the morning. But then one thing said I had to do it at the same time ever day and I have to be asleep for at least 3 hours? I'm confused. I wake up when my husband does then go back to sleep so some days it's only like 1.5 hours between but I don't want to rely on testing when he wakes up cause he doesn't wake up the same time ever day?! Also what do I look for for ovulation? Thanks!