Are you trying to get your money back because there was a problem with a purchase?
If so, you need to report a problem with the transaction and open up a dispute which will then be mediated by EBAY. During the reporting process, you'll be able to narrow down what the issue is and add your own comments. Once opened, notification will be sent to the seller who will be given time to respond. If during the process, the seller fails to respond, or you're simply not satisfied with how communications are going between you and the seller, you'll be able to escalate the dispute into a formal claim.
At this time, Ebay will step in and review the claim. Ebay will make a final determination and if you're sided with, a refund will be issued (if everything meets the requirements for purchase protection).
If you're asking an entirely different question, you'll need to be more specific with the details.
