Step 1: Login to the cPanel.
Step 2: Open File Manager menu located in Files section.
Step 3: Navigate to the root folder of the Opencart installation, right-click on config.php and used Code Edit option.
Step 4: Open the file and edit its source code online. You will need to locate and edit the admin and website URL’s.
Step 5: Now, locate and edit the config.php file located in the /admin folder inside the Opencart installation. You can use Code Editor for editing as well.
Step 6: Replace all the outlined URLs with the new domain name you would like to set for the Opencart installation and save the changes.