From the Main Menu Bar, click on Events / Combined Events to display the Combined Events Menu. After an 11-12 Girls Pentathlon Combined Event is added, the lower half of the screen might look like the following with the entire event list at the lower left:
You can click and drag an event to the right panel to include in the new Combined Event or just position the cursor on a event and double click it to move it into the schedule. After a few events have been moved to the right, the window might look like this:
The events on the right can be in any order regardless of the event number. You can drag any event in the schedule and drop it onto any other event in the schedule to switch the order of the two events. To remove an event from the right, double click the event.