Gantt Chart - Add a Summary Task

Open your plan and click on Delivery / Gantt Chart. 

1. Select the Gantt Chart page under the Delivery Plan tab.
2. Summary Tasks are created by converting a Task or a Milestone when adding subtasks.
3. Subtasks can be added in several ways: 
   1. Right click on the row you wish to convert to a Summary Task and in the context menu, click Add -> Subtask
      
       
   2. Dragging a row onto the Task will add it as a Subtask. The row will be highlighted when it will add the row as a Subtask, rather than a redline to show it will be re-ordered above or below