Note: Only admins and hub owners can modify the schedule and therefore use this feature.
All phases of a tree element can be transferred to the plan or actual/forecast columns by right-clicking on the desired tree level (measure, measure package, project or program) and then selecting "Transfer values... --> Set workflow actual/forecast or plan".
Additionally overwrite all existing values
If you want to overwrite already existing values, you may check the corresponding option and agree.
Additionally include all started worklfow phases
If you want to include already started phases, you can select this corresponding option.
More detailed information on managing workflows, processes and phases can be found here.