An automation must contain at least one initiating event to execute. The event can originate from interrogated controls, adapters, entry points, and Windows form/App Bar controls.
After you have identified the initiating event, you drag the event from the Palette to the Automation Surface. A design block is displayed on the automation to represent the event. Here is an example of a design block for the Click event of an interrogated button:
Events are designated by a green E icon. Note that event blocks do not have input event ports and the only data that can be sent from an event is the sender object.