Do I take it you wish to make one and not receive one, your post is not clear.
To make one under Managed Payments, click on the item sold, then click on the highlighted item number.
Top left from the big blue button, mine there says Feedback, drop down menu click on refund.
Enter the desired refund, select a reason for that refund, and submit.
Probbaly best to use a desktop browser here, and not the app.
