In your dashboard, you can update your availability by clicking on "Calendar" - in the calendar, white days are available, grey are unavailable and red are already booked (through Airsupply).
You can click on any date to make it unavailable and then press "Save". The date will change to a grey colour, indicating that you are not able to take any teaching roles.
You can also select multiple days and click on the toggle at the bottom of the page to move these days between available and busy. Press "save" and the selected dates change colour, letting schools know whether you are available or not.
Please note that you will NOT be offered any roles during time you have marked yourself unavailable.