You can add products to the Amazon Marketplace catalog one at a time, or if you have a Professional selling subscription, you can add large batches of items using bulk tools.
Two ways to list products
1. List products already on Amazon.com
Indicate how many products you have to sell, condition of the product(s), and shipping options
2. List products not yet on Amazon.com
- Identify UPC/EAN and SKU
- List products attributes - for example title, description