At main menu click on Settings >> Payments tab
Payments settings
Show "Paid" image on fully paid invoices: make it checked if you would like to display a "PAID" or other logo on fully paid invoices.
Invoices only with "Paid" status will display "paid" logo. Use the "Mark invoice as paid" button when invoicing and make checked the "Paid in full and close the invoice" option to change the invoice status to "Paid"
Send Payment Receipt email after each payment recorded: automatically generates the payment receipt and opens the payment receipt email window after a payment record added for the current invoice. Optionally you can attach the invoice with updated balance to the payment receipt email. You can customize the payment receipt email body under the Email templates tab
Insert PayPal "Pay Now" button: make it checked if you would like to display a "Pay Now" button on unpaid or partly paid invoices.
You customer can pay instantly with PayPal for the remaining invoice balance. You need a PayPal business account to use this function and after you need to setup PayPal settings by clicking PayPal toolbar button under the invoice email window.
PAID image for invoices: you can use your own paid logo image, just click on load logo image button and browse for your image file (BMP,JPG or PNG image files accepted).
You can restore the build-in paid logo image by clicking on "Restore default" button
PayPal image for invoices: you can use your own button image for PayPal payment button, just click on load button image button and browse for your image file (BMP,JPG or PNG image files accepted). You can restore the build-in PayPal button image by clicking on "Restore default" button
Payment receipt text labels: if you would like to change the various texts that appear on the printed invoice, modify these values.
When you've finished editing the fields, click on "Save settings" toolbar button.