One of the most important things every music creator can do for themselves is protect their intellectual property. By technical standards, a work is copyrighted once it's been made into a tangible form. However, officially registering that work by submitting it to the US Library of Congress
provides very valuable protection should anyone ever infringe upon your creation. The process isn't too bad once you've been exposed to it and have some education in the field. It's simple enough that you can definitely embark on doing it yourself, or if you'd like some assistance to make sure you've done it right the first time (it is a government document, after all), you could always request the assistance of a music business professional or copyright lawyer. But in the meantime, here's a step-by-step guide on the basics of how to copyright a song.