You can make changes to an item link from the Linked to item section.
1. In the Product Backlog, Quality Assurance, or Planning view, select a linked item.
The Linked to item section at the bottom will update to show links related to the selected item.
2. In the Links list, find the link that you want to edit and click the arrow to display information about the link.
3. Edit the values in one or more fields.
Changes are saved instantly.