If you combine several activities which are logically connected and need to be finished within the same time frame, you create a summary activity.
Proceed as follows:
ATTENTION The duration of the summary activity is calculated based on the start and end dates of the subordinate activities. I.e. that a summary activity starts on the start date of the earliest subordinate activity and ends on the end date of the latest subordinate activity. If you change the start and/or end dates of the subordinate activities, the duration of the summary activity is automatically adjusted.