Canceling is pretty easy.

Go to www.Recreation.gov, and click on My Account or Log-In. (They both bring up the Member Log-In window). And sign in.

You will get an Account Overview page, and on the left some choices. Two of the choices are:
  • Current Reservations
  • Lottery Applications
By the way, the Lottery Applications... Detail will give you a printable page of the choices you entered on your application.

Once you get a successful reservation in the lottery, it will appear under the Current Reservations link. If you go to Current Reservations... Detail, it gives you the choice to Cancel Reservation.