If you want to define Per-Product Meta-Tags go to the Catalog -> Categories -> Products list. Find the item that you want to change and then look for a symbol resembling BMW’s mascot in the Action column.
The new page will open. All you need to do is to fill in the details and click on the Preview button, and then on the Update button.
Please, note that the metatags must be relevenat to the product entry, otherwise they will loose their benefits in usage.Defining Meta Tags for the Products,