In an activity diagram, a signal send can be used to replace an event label on a transition.
Unlabeled transition arrows connect the Signal Send shape to the previous and next action states. You can also use a dependency to connect the point to an object representing the sender of the signal.
Name a Signal Send shape and add other property values
Open the element's UML Properties dialog box by double-clicking the icon that represents the element in the tree view or the shape that represents the element in a diagram.