Ok, note that registration is not "required", but HIGHLY recommend. Once you record it, is is yours, you own the copyright to it. But to enforce the copyright, registration is recommended. On that note:
To register a work, send the following three elements in the same envelope or package to:
Library of Congress
Copyright Office
101 Independence Avenue, S.E.
Washington, D.C. 20559-6000
1. A properly completed application form.
2. A nonrefundable filing fee of $30 for each application
3. A nonreturnable deposit of the work being registered. The deposit requirements vary in particular situations.
If the work was first published in the United States on or after January 1, 1978, two complete copies or phonorecords of the best edition. If sending multiple works, all applications, deposits, and fees should be sent in the same package. If possible, applications should be attached to the appropriate deposit. Whenever possible, number each package (e. g., 1 of 3, 2 of 4) to facilitate processing.
SUBMIT FORMS IN BLACK INK OR TYPED PRINT ONLY!
There are different forms, dependent on your role:
Form PA: for published and unpublished works of the performing arts (musical and dramatic works, pantomimes and choreographic works, motion pictures and other audiovisual works)
http://www.copyright.gov/forms/formpai.pdf
Form SR: for published and unpublished sound recordings
http://www.copyright.gov/forms/formsri.pdf
Each of those forms come with detailed instructions on the whole process. You can also complete the forms "online" and then print them out and mail them in per the requirements if you don't want to fill them in by hand. Here are the links to the forms you can fill in online:
Form PA:
http://www.copyright.gov/forms/formpai.pdf
Form SR:
http://www.copyright.gov/forms/formsri.pdf
Note for printing, the submission forms ARE TWO SIDED. Print page one of the application, flip the paper, print side 2. Make sure that the top of the page of each page is head to head. Be sure to do this, if your applicatoin is not submitted to specs, they will reject it, and you lose your application fee as it is nonrefundable.
Let me know if you have any more questions.