You have to convert the task, bug, etc, to a "Product Backlog Item".

1. Click on the item in the "Work Items".

2. Over to the far right is a three-dots icon, click on that.

3. Click "Change type...".

4. Choose "Product Backlog Item", and give a reason if you wish to.

5. Click "Ok"

6. Update any parameters it highlights in red.

7. Click "Save".