When to start the pill??

Kyle`
So I recently got my birth control prescription. I haven't started taking it yet. My doctor said that I should take it the Sunday after my period. But I also saw that you can take it the first day of your period, or whenever you want to start it. Does it matter when I start? And also, my period should start in a day or so, but if I take it today, will I still get my period or will it skip it or something? Sorry for so many questions 😖😫