To add a transition to your DES, first make sure you have added the events for the transition. Then click either the line or curve transition buttons in the toolbox on the left.
To start a transition, click and hold on the start or from state of your transition and drag your mouse cursor to the stop or to state. You will notice a transition line follow your mouse cursor until you release your mouse click at the stop state. Now the transition line will connect the two states. If you only click on your start state or drag your transition line to the same start and stop state you will create a self-loop. Once you place your transition line, the DES Transition Editor dialog box will appear.
This is where you select the event for the transition. If you click the Self-transition checkbox, a self-loop will be created and your To state will now match your From state. When you are done selecting the event, click OK and the transition will be added to the Transition pane. You will also notice a new label appear next to your transition line with the event name you selected.