Hi Eric,
Amazon.com has a step-by-step guide for sellers at Link hidden: Login to view
For new sellers outside the UK/France/Italy/Germany, you only need to open a seller account in any of these Amazon’s European marketplaces, and you’ll be allowed to create offers on these platforms.
from
Link hidden: Login to view
Amazon has a "Bestsellers List" which is updated hourly, which reveals the bestselling items. With this page you can discover the best in Amazon Best Sellers and also find the top 100 most popular products/categories at Amazon Link hidden: Login to view
Please note that clothing is among the products that require pre-approval from Amazon before listing. (Other items/categories that need pre-approval are Beauty, Gourmet, Jewelry, Personal Computers, Shoes & Accessories, Watches and Wireless Link hidden: Login to view)
You may contact Amazon at Link hidden: Login to view
Hope this helps. Welcome to SaleHoo! :)