How do I lock in my business name and what additional paperwork do I need?

I assume that you mean that you have registered your dba in Florida, and/or in the particular municipality in which you are located, which offers you very little protection, if any, outside of the jurisdiction in which it's registered, and not that much inside.  Since you are just starting, I assume that your dba would not qualify as a common law trademark yet.  The best protection you can get, and it is not absolute, is to register trademarks for any marks you want to protect, including your business name.  You don't need a trademark to sell your own jewelry; trademarks protect various names or symbols which are associated with your business from being misappropriated by others.  For example, McDonald's doesn't want someone using golden arches (which might techinically be considered trade dress, not trademarks, but it's the same concept) to promote a fast food restaurant; that person woudl be trading on a mark which McDonald's has spent time and money building up to represent a particular type of restaurant with particular qualities.  You may, however, need various types of licenses, depending on the jurisdiction in which you will be operating.  Finally, I don't know your particular situation, but as a general rule I'm aware of no reason why you would have to reside in the US to operate a business here.