I just registered and want to add lyrics to a band's songs (there are currently none). Do I need a certain number of posts before I can do this? Otherwise, I can't figure it out how ...

Click on the "edit" icon (pencil) right below the band name/album title, then click on the "lyrics" icon (scroll) next to each track and add them there. Please save all of them at once, not one-by-one.

Any registered user can add new information. Only veteran users can edit existing data. See: http://www.metal-archives.com/content/help#tab_ranks