From tab "Task", you can edit the planned start and finish dates of your task. If the element is an activity, so if there is a level "task" under the level of the element in the WBS, the planned start and finish date is automaticaly set by the planning of tasks under the activity.
Business Value allows you to set the value of the activity.
"Use Iteration" allows you to set the planning automaticaly using time boxes (see chapter about iteration)
Once the task realy begin, you can change the state of your task in Monitoring Panel.
The monitor panel will show you warning about mismatch in your planning.
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