This page shows all of the payment information for any given entrant. A new payment may be entered at the bottom of the page. Dates are all specified in the Database Format Year-Mo-Dy, so that 2016-06-10 is June 6, 2016. A 4-digit year is required, as are the dashes. Month and day can be single digits - 2016-6-10 for instance.
Selecting edit on a payment will permit you to edit that payment. Setting the payment amount to zero will delete the payment from the database.