When do I need to start my birth control?

Hannah • {aspiring coloratura soprano} •vocal performance major | APSU Gov '21• Eli <3

Hey everyone! I’m just now beginning to start my birth control. I haven’t actually taken it because I’m confused on when I should start taking it. I read that you start your first pill the Sunday after your period starts. But, the doctor that gave it to me told me to start it immediately. What should I do?