@FranchisePaws
Set up a 'note receivable' (other asset or other current asset) account. Confirm that you have an interest income (other income) account set up. When you receive the payment, create a deposit, assign the principal portion of the payment to the note receivable and the interest portion to the interest income account. This will reduce the balance on the note receivable on your balance sheet and book the interest received to 'other income' on your P&L.
Any payments received that were recorded to the liability account, need to be reassigned as described above. Then, delete that liability account.