The fastest way to find the detail of a specific payment is to use the search on the payment overview page. Just enter, for example, the amount, the customer's e-mail or the payment ID into the search field. The matching results will be displayed and one click takes you straight to the detail of the selected payment.
You will find the list of all payments (called e-payments in the old interface) in the left-hand menu in the Payments section. This page offers advanced filtering and search options that make it easy to look up the transactions you need.
You can also refund payments quickly straight from the list – there is no need to open the payment detail.