In order to submit a registration with TuneRegistry, you must have the proper authority.  
To have proper authority, you must either own or control the copyright in the work that is being registered. A work can be a Song, Recording, or Release, depending on the type of registration.

For example, if you want to submit a U.S. Song Registration, you will need to own or control the copyright in the Song that is being registered.  To submit a Music Metadata registration, you will need to own or control the copyright in the Recording that is being registered.

In general, you own a copyright if you were a creator/author/artist and did not transfer your rights via written agreement.  In general, you control a copyright if you have a written agreement signed from the owner of the copyright granting you authority to administer the copyright on their behalf.