In Final Draft for Windows, go to File > WGA; in Final Draft for Mac go to File > Register Script. If your computer has an internet connection, you will be taken to a page on our website with a link to the Writers' Guild of America, west's registration page. Final Draft is a preferred file format and the only screenwriting software to integrate WGAw Online Script Registration.
Please note that registering your script with the Writers' Guild is not the same as a US copyright. If you also want an official copyright, this is done through the Library of Congress.
Click HERE to go to the website of the US Copyright Office.