It is a federal jurisdictional requirement that, before you can even file a complaint for infringement of copyright, it must be registered with the Library of Congress Copyright Office. Registration of most works can be done by YOU, the publisher or creator . To protect a work it must be properly registered. Yes, you can register an unpublished work and even keep its existence a secret, while protecting it through registration. Second, obtain the proper form.
Forms are available free, online with complete instructions.
A TX is also used for registration of source code of a computer program. Use a VA to register a work that mainly are of the visual arts, like drawings, photos. Use a PA to register a musical composition, which can be written sheet music or a recording. One can register an album or song collection recording however it is wise to either register each song or to be sure to list all songs carefully on the album. There is even a form MW for a chip mask work.