In the step "Availabilities" when you create your listing, you can indicate the minimum number of nights. To rent per week, please indicate "minimum 7 nights".
It is possible for you to add a condition, if by instance you want to rent minimum 1 week during the summer and 2 days remaining time.
The price in "Price options" must correspond to the price you are asking for the entire place per night ! Please do not indicate the price per person per night.