You access this feature using the pupil payments list. For help accessing the pupil payments list see Recording & Tracking Pupil Payments.
This feature is primarily aimed at your instructors as part of the their day-to day management of and contact with their pupils. As an administrator you of course have full access to this feature and it behaves in the same way as it does for your instructors. So for a comprehensive guide you should read Instructor Documentation - Pupil Payments.
See Instructor Documentation - Purchasing a Block or Course for a comprehensive guide.
See Instructor Documentation - Adding a Credit or Redeeming a Voucher for a comprehensive guide.
See Instructor Documentation - Adding a Charge for a comprehensive guide.