Setting up special prices (discounts, etc.) is easy with osCommerce. To define a special item, you should login to your osCommerce admin area, go to Catalog and select the Specials link from the left column. Then click on the New Product button under the special products list.
You will be prompted to select an item and create a special price for it. You should also enter an expiration date – this determines until which day the discount will be active.
After you have filled in the details, you should click on the Save button. The new special item will be immediately included in the list.