Product's appearance and its relative order may be managed in the Order tab.

Each of the available fields is described below:
A product's display order relative to other products listed on the checkout page, may be set by dragging and re-arranging the products as they appear on your screen. Simply mouse click on the product name and move it up or down relative to the other listings.
A showcase product appears at the top of the checkout page with a large image highlighting the product relative to other listings. There can only be one showcase item for each checkout page.