How do I add related items to a product for up-selling and cross-selling purposes?
You can go to Products then edit a product. In the Product Options section choose the number of Related Products you would like for the item and hit Next. On this page you can choose the related items for this product.
You can also go to Products, click on the product name then scroll down the product detail screen until you see Related Products. Click Add, select the number of items you would like and click OK then choose the items from the Related Products screen