Unfortunately, due to advanced and profound improvements implemented in our osCommerce 2.3.1 templates in comparison with clean/default osCommerce 2.3.1 engine, unique and special features in some of our osCommerce2.3.1 templates, it’s not possible to create generic instructions on installation osCommerce 2.3.1 templates over the existing store.
At this point, we strongly recommend you to perform clean installation of your osCommerce 2.3.1 template to avoid any issues.
If this option is not acceptable for you under any circumstances, please submit your request to our Support Team at: http://esupport.template-help.com/index.php?/Tickets/Submit
Please, use “osCommerce. Installation Over Existing Shop” as ticket subject.
Note, you will need to provide us with your PHPMyAdmin tool access details, FTP and admin panel login details.