Your nightly rate is entered when you first list your Rental and is under Rates. Under Rates you can edit your nightly rate, as well as add a discount, request a deposit, add additional fees, taxes and set your cancellation policy. 

Under Availability, you can override your nightly rate to allow a new rate for a specific day or longer lengths of time without affecting your default rate. 

Changes you make to your rates do not apply to upcoming reservations that have already been booked and accepted.