One of the item settings is to select a part of the image that, when clicked by a participant, will end a display of this item. This option is turned off by default, but to run it, please click “turn on” and drag over the image to map the clicking area (it can be the whole image, simply click the "Select all" button).
You can always change the chosen area as many times as you want before running a study (or after reverting it to a draft).
NOTE: For the finish on click and the finish on keypress options, you can set a minimum display time (it shows once you set at least one of the item display finishing options). If you set this time, i.e., to 5 seconds, that means clicking/pressing a key won't work for the first 5 seconds of the item display. It can prevent skipping the item too fast by participants.