Creating a Brand?!

Took a break from amazon for a year and come back to it. I have some stock and normally you “jump” into listings to get a few orders (friendly competition) aswell as your own listings. But now every listing has a “brand” so you have to be authorised to sell it? Clearly unbranded generic products with just the brand name in the title at the end. How is this done? Half of the products are from China also.

My question is how do I register the brand and do I really have to trademark it?

Thanks