This feature is available in Enterprise and Ultimate editions.
You can update your backlog directly from the Team Scheduling page.
Go to Release Planning > Team Scheduling.
In the Backlog grid, click on the backlog item you want to update. The Details page for that item opens.
Click Edit to open the Backlog Item Edit window and update the backlog item details, then click Save, or click Show Relationships to associate other items with it (e.g., add tasks, tests, links, and attachments, or assign requests and issues). See Backlog for more details on all you can do with backlog items.