Go to Families > All Families, search for the family and click the Row Menu icon. Then select Accept Payment/Post Credit.
Open the Family page and select the Payment/Credit button.
Enter a Trans Date (payment date) if different than today, a Method, a check number if appropriate, and the amount in the Payment field if different than the Current Balance.
Complete the remaining fields if appropriate (Subtype, Note, Chk#).
Select the Save Payment button (or Save & Make Another Payment) since this is a "Cash, Check, Other Credits" Payment and not an ePayment.