Opk and BBT help

Jessica

I've started tracking my bbt a few days ago, just to get a head start. My period is 4 days late but I am not pregnant. Not sure why it's late though?

Anyway I'm not sure if I'm regular or anything how do I start using opks? Do I start on a specific day and test daily? For my BBT am I looking for a rise in temp, leading up to ovulation and then a drop in temp for ovulation. I'm so confused? What do I look for and how do I know when to start BD?