taking the pill

Could you please tell me specifically how to take microgestin 1.5/30 21's ? They are the 3 week pills. I'm used to taking one everyday. Do you take them for 3 weeks and then take a week off, or do you continue to take them until you're on your mentstrual cycle and taking that week off. If waiting until the menstrual cycle to take the week off, what if you start your cycle on a Saturday and end on Tuesday.

Could you just give me some specifics?

Thank You,

Heather