How do I create a customer Prepayment?

1. Select Tasks, Receive Money.
2. Click the magnifying glass to select the Customer ID.
3. Select the Apply to Revenues tab, and select the Prepayment check box.
4. Enter a Description and the payment amount.
5. Enter a unique reference number for this transaction.
6. Enter a Receipt number (if not automatically assigned).
7. Click the Save button.

How do I apply a customer prepayment to an invoice?