You can do it two (maybe three) ways. The first is you commit to shipping it out, and give them a time frame you’ll ship within, then list it on Amazon. This means you handle sales when they come in and Amazon just takes a cut of the payment. You update your inventory and keep your seller account up to date. The other would be to have it fulfilled by Amazon which means you just ship them product in large quantities, pay them a bit for the storage, packaging, inventory, and shipping (which they have rates defined for) and then they handle it from there and pay you when it sells. This is how you can qualify for Prime shipping and things like that. It can get a little expensive, but it takes a lot of the process of running a business off of you and puts that on Amazon. It’s pretty amazing how well they do. Amazon does stock items that they purchase directly, just like grocery stores or Walmart, but mostly those are really big complicated deals with known manufacturers. You’d usually want to have quite a bit of sales before approaching them to stock your goods. That’s not to say they won’t, but the above options would give you a lot more control on things like pricing and how many you’ll deliver. Unless your brand is pretty far along, I’d pick the option above that fits your needs better. I think Fulfilled by Amazon is one of the best deals I’ve ever seen, so that’s what I’d recommend, but check the others out and see what works for you.