When using WBS Summary Activity types….
The WBS Summary activity type should be a fixed duration type. Either fixed duration & units or fixed duration & units/time. Set-up on activity general tab.
On the WBS Summary activity type the activity % complete type should be set to physical so that the PM can manually update the progress of the project. Set-up on activity general tab.
If a Start milestone is being used, that must be marked started. The WBS Summary activity will pick up this date as the earliest start date (Assuming there are no other activities).
If a Finish milestone is being used, that must have a Finish On constraint. Since the WBS Summary will be a duration type activity, it needs to look at the earliest start date and latest finish date to accurately calculate original, actual, and at complete durations prior to the activity being started.
You can assign all of the resources to the WBS Summary activity.
Physical % Complete of the activity can be updated after actuals are applied.