Adding event messages to a sequence diagram
You can add Event messages to a Sequence Diagram through the Sequence Diagram tab or through a drag-and-drop operation.
To add an event message through the sequence diagram tab:
1. On the Sequence Diagram tab, click the 
Event button.
Event button.2. In line with the required Statement, click the lifeline of the source object or System Boundary.
3. Click the lifeline of the target object or System Boundary.
4. From the Selection dialog, select the required Event, and then click OK; or click the New button.
Modeler adds an Event message to the diagram.
5. If you want to set instance properties of the Event message:
a. Right-click the Event message, and then click Instance Properties.
b. On the Options tab, specify the Actual Parameters and Latency as required.
To add an event message through a drag-and-drop operation:
1. Open the Sequence Diagram.
2. From an appropriate pane, drag the Event you want to add to the source object or System Boundary.
3. From the context menu, click the target object.
Modeler adds an Event message to the diagram.
4. If you want to set instance properties of the Event message:
a. Right-click the Event message, and then click Instance Properties.
b. On the Options tab, specify the Actual Parameters and Latency as required.