In order to configure osCommerce to work with SSL please open the file public_html/catalog/includes/configure.php and make the following changes:
define('HTTP_SERVER', 'http://www.yourdomain.com'); // eg, http://localhost - should not be empty for productive servers
define('HTTPS_SERVER', 'https://yourdomain.com'); // eg, https://localhost - should not be empty for productive servers
define('ENABLE_SSL', true); // secure webserver for checkout procedure?
define('HTTP_COOKIE_DOMAIN', 'www.yourdomain.com');
define('HTTPS_COOKIE_DOMAIN', 'yourdomain.com');
define('HTTP_COOKIE_PATH', '/catalog/');
define('HTTPS_COOKIE_PATH', '/catalog/');
define('DIR_WS_HTTP_CATALOG', '/catalog/');
define('DIR_WS_HTTPS_CATALOG', '/catalog/');
Similar to the above changes have to be made in the file public_html/catalog/admin/includes/configure.php which is responsible for the admin area configurations.
In the above example we are configuring an osCommerce installation in the catalog directory with domain yourdomain.com. Please adjust the above settings to your details.