I don't understand how to do the Shopping Cart's phpMyAdmin alterations!
Open your phpMyAdmin, this is usually done through your Hosting service Control Panel. Once you have phpMyAdmin open, click your shopping cart's database on the left side. You will see on the left side the name of each and every table, on the right side you'll find several tabs to conduct various tasks.
Click the tab on the right that say's "SQL", enter the Alterations required for your particular shopping cart. For example if you have Zen cart installed you would add:
ALTER TABLE `zen_products` ADD INDEX `idx_products_image` ( `products_image` );
Notice the zen_ prefix for products above, if on the left side you have no prefix, or something different then you need to modify the above to match you installation prefix. Once your prefix matches press the "Go" button. This will alter the specific table mentioned.
For whichever shopping cart you use, these alterations to the database only needs to be accomplished one time. In fact if you attempt to do it more then once you will recieve an phpMyAdmin error "Duplicate key name...."