How to use BC

Hi girls! So I am new to birth control haven't started it because I don't know how, and to make an appointment with my doctor takes forever. So I haven't started my period just yet (haven't gotten a period since my MC Jan.6) and I read that I should take it a Sunday after my period begins. But I don't want to wait idk when I will get my AF so I just wanted to know how it worked. I have the Trinessa pill.