The Add Existing button to select and existing resources from the model.
Add time periods as table columns by clicking the Time Period button. In the opened Time Periods dialog fill in these properties:
Select or create a Timeline package to store the Forecast dates.
Select the Forecast Kind: Specified Periods, Periodic, Specified Dates.
Select Time Periods by clicking in the Time Periods property value cell.
Enter the Subjects of Forecast by clicking on the cell under time period column. In the Select Subject of Forecast dialog select the Resources, Standards, or Protocols to forecast.