(1) Go to Extension->Extension installer and click "Upload".
(2) Select the correct modification file from your local drive and click "Open".
(3) After you verify that the upload is successful, you need to navigate to Extension > Modifications and click the refresh button.
(4) After successfully applying the modification, the system will notify you with a green success message.
Disclaimer: This page has been adapted from the official OpenCart website. The OpenCart logo is the property of OpenCart.