Check with your jingle house to find out your status. Many companies who employee jingle writers offer "work for hire" agreements. This means you are hired to write the jingle, but the company owns it when you are finished. If you are under a work for hire agreement, you cannot copyright your jingle.
Download form PA. The Library of Congress uses this form to protect lyrics and melodies. Fill out the form completely. Most of the questions are about who wrote the song and where to send the completed certificate. Be sure to include any alternate titles for the jingle, and include any co-authors.
Fill out form CO. This copyright form is to protect the sound of your recording, not the words and lyrics. This means if you have a recording of the song, you own the production. For example, if someone re-recorded it, they would own their recorded version and you would own yours. You would still retain the copyright to the lyrics and melody if you have filed a form PA.
Enclose one copy of your jingle for each song. The most common copy is a CD. You can include sheet music or cassette or any other representation of your song. You only need one copy for each form you filled out.
Enclose a check to pay the copyright fees. The fee for form PA is $65. The fee for form CO is $50. You can write one check for the total amount of fees you are paying if you put both forms and two copies of the jingle in one package.
Open your certification when the Library of Congress mails it to you. You will find two forms of copyright in the package -- one for the lyrics and melody, and one for the sound embodied in your recording. Keep these on file as your proof of copyright.