The first step to change the dates on your applicaiton/reservation is to go to your "My Page"
Step1: click on the "My Page" icon at the top of the site.
Step2: click on the "My Reservation" tab on the left.
Step3: click on the "Modify" button to bring up a new page with your application's info on it.
After clicking on the "modify" button, this is the page that should show up and will allow you to change your schedule and preferences (Note! make sure you click the submit button afterwards to save your changes!):