Amazon FBA question

I recently found a fast-growing product from a well-known brand that is NOT listed on Amazon. How do I go about selling this product on Amazon?

Use a tool/program to see what my margins would be after fees and such? Buy stock of the product first? Should I get an LLC to buy wholesale?

Also, would there ever be licensing issues? (i.e. a certain company wouldn’t want you selling their products on Amazon)