Many people get completely confused about registering copyrights. They believe in nonsense spouted around the Net, or water-coolers, about the "poor man's copyright," for example (mailing yourself your manuscript) and stuff like that.  Don't do that. Just ake your finished manuscript and register your copyright at the ECO, the Electronic Copyright Office.  It costs around $45.00 (Forty-Five Dollars USD) as of 2019, it's fast and easy.  You can read the Copyright Office's handout, right here: Registering Your Copyright online

Pseudonyms

Lots of folks ask, "can I register a copyright in my pseudonym?" to answer that question, read the attached handout about using pseudonyms from the US Copyright Office.   Using a Pseudonym To Register your Copyright