Once a credit note has been printed, you then need to issue it. Once it has been issued the credit note will appear on the customer's statement screen and can then be used. A step by step guide can be found below the video.
Steps
Open Sales Invoice Manager.
Go to the Credit Note Print stage.
Green select the credit note(s) that have been printed and require issuing.
Use the Actions menu to select Move Next.
In the Issue stage, green select the same Credit Note(s).
Use the Actions menu to select Issue Credit Note. This will update the accounts and the customers statement.