Starting nuvaring for the first time ever!! help never been on birth control

Helloooo everyone, okay so basically i’ve never been on birth control before and i went to a gynecologist appointment today and she prescribed me the nuvaring and told me i have to insert the first ring in the first day i get my period this month and leave it in for 3 weeks and then take it out the same day i put it in so let’s say i get my period friday i would have to put it in friday and take it out 3 weeks from that friday and then i would get my period again and the following friday i would have to put a new one in. My question is if that is correct because i’ve heard that you aren’t supposed to have the nuvaring in while you’re on your period?? help pls i’m so clueless right now i’ve been googling since it’s the first time i’m going to be on any birth control i want to get it right. thank youuu