Whole sale company

Hello, I’m new to this selling on Amazon and I’ve seen YouTube videos saying that in order to sell certin products, you need to show Amazon you have a partnership with a company you buy your bulk in . The sites that were given in the videos I’ve seen won’t allow me to create an account every username I put in it says it is good then once I hit next to finish the set up account it tells me my username is not valid etc .

If anyone could please list some good ones I would greatly appreciate it . I’m looking to sale a variety of things but I’m starting out with coffee bags .