From the 'Ringback Tones' section, click MORE INFO.
Click Manage Ringback Tones.
Click My Ringback Tones.
Click Create Your Own Playlist.
Enter a name for the playlist.
Select the desired Ringback Tone(s) then click Apply Changes.
Selected when a checkmark is present.
Delete a Playlist
These steps only work for an unassigned playlist. To unassign a playlist, drag it from the contact or group (on the right side of the screen) then drop it on the Ringback Tones section (on the left side of the screen).