In my Dashboard, I can click on "View":

Then I land on "My reservations", I then click on "Details" in order to cancel atraveler's reservation.

At the bottom of the page I will see "Cancel Reservation". 

Obviously, if I have to cancel, the sooner the better. I have to keep in mind that my cancellation will have consequences on the guest who may be penalized by it. Indeed, it is not certain that he will find a host on time and he will have organized his vacation according to my land. I therefore explain the reasons for my cancellation.