Change Assignee
To change the Assignee, you will need to edit the content item.
View the content and look for the "EDIT" button at the top right. If you only see the Follow/Unfollow button and don't see an Edit button, then you don't have permission to make changes to this item.
Permission: To edit content, 'member' users will need to be the existing assignee or in the relevant module-level manager group. A user in the 'Staff' group can edit any content.
(Note that you may lose permission to edit the item if you are no longer the Assignee)
You may also be able to change the Assignee for multiple items at once using Bulk Actions.