Preassignments are added to a schedule when the "Create..." button is clicked in an MSP installation to make a new schedule. If you want to add preassignments to a schedule after it has already been created, you have two options:
Add the preassignment directly to the schedule.
This can be done by adding a volunteer to the first instance of the preassignment in either an MSP installation or in the Admin view of the Web Terminal, and then clicking the "Repeats..." bubble to create a new preassignment. This will add the preassignment to the Preassignments pane, as well.
Add/edit the preassignments pane.
If you have already added a preassignment to the Preassignments pane and you want to apply it to a schedule:
In an MSP installation, open the schedule and then minimize it. Go to the Preassignments pane and edit the preassignment. Make no changes and click “Save”. It will now prompt you to add it to the open schedule. This is especially helpful when you have multiple schedules already live and need to add the preassignment to each of them.
In the Admin view of the Web Terminal, go to the Preassignments pane and edit the preassignment. Make no changes and click “Save”. It will now prompt you to indicate which schedule(s) the pre-assignment will be added to.