I am not an attorney, but under U.S. Copyright law, your self-published work is protected the moment you write it, or type it onto a page (or a hard drive). If you feel more comfortable or secure you can register your work before you send it out. However, people in the publishing industry know this is the law, so as long as you’re dealing with reputable industry professionals, you don’t have to worry that they’ll steal your work and try to pass it off as their own.
Welcome to Ask Angeline. My mission is to help self-publishing and indie authors share their God given message with the world.