The following article shows how to bulk change the items on your work board.
Sort your Work list to view just the tasks you'd like to bulk change.
From your Work board, select Actions.
Select what you want to update.
Tick to select the items that you want this to apply to.
Depending on your choice of action, you can select the due date, select a user or select a status to update all the records selected on the last page.
Update Due Date
Update Assigned User
Update Status
