Should A New Pack Of Contraceptive Pills Be Started Only After The Menstruation?

I was wondering about how to correctly take my birth control. Im a little confused. It says take first 21 days of active pills then restart a new pack of active pills on day 22. Do not take the last 7 placebo pills. So after I finish my current pack do i just start a new pack or wait for my menstraul period or automatically start a new pack?