There are a couple of ways to do it, I've noticed....

One is to post the lyrics to the Mudcat Forum. A quick scan will reveal threads with the heading "Lyric Add," and the name of the tune to which the lyrics pertain. As a guideline, you could click on one of these headings and note how other people have done it. Be aware that to get the proper formatting for verses and such requires the use of html tags, such as
for the line breaks; otherwise the lyrics you post will run together in a jumbled mess that makes it very hard to read (experience is the best teacher).

Another way to do it is to go to the box marked "DigiTrad Lyrics Search" and click on the pull-down menu arrow. Select "About The Digitrad" and click "Go." This will take you to a page that has a lot of information about the Digitrad data base. Under the "Official Rules" blue clicky thing Dick Greenhaus lists an email address to where you can send lyrics. Try this first to go there now, but in case it doesn't work or for future reference the e-mail address is: digitrad@world.std.com