Reservation of apartment

Hello.

I have a question. I want to rent my apartment only on saturdays and only for 7 night (check-in on Saturday after 3 pm and check-out next Saturday till 11 am). I have changed the number of the nights (7) on my profile, but I can not find the way how to change the exact dates (on Saturday, evru 7 days). Can someone help me? Thank you.