How do I copyright a fictional character I created to secure rights in USA to develop a comic & a film?

I have created a story with 3 main fictional characters that i wish to copyright and have the rights to produce a comicbook and a film to sell and distribute in the USA. I need to know the steps to register the characters and the story so I have the rights or I can sell the rights for production of a movie, comicbook, tv series, etc. in the US. Also to be able to sell merchandise or give rights to licencees to manufacture products. I do not live in the USA.