Good afternoon Tannis!
In your transaction entry screen, you will want to make sure that your Transaction Type is set to Deposit at the top of your screen, and that your credit card is selected as the bank account. Fill in the rest of the screen as normal (date, reference, description, and total).
You will select EX as your type (assuming that it was originally an expense), and select the expense account that the item was originally purchased against. This will auto-fill the line as a negative number, showing that you are reducing the expense due to the return. You can use the tax codes to deal with any GST - just make sure the GST is also negative.
This should deal with everything you need to. Let us know if you have any further questions!
