I'd recommend at least looking at all of the help topics before you go very far. There's not that much to learn.
The Song List Window
When you launch The Digital Tradition, the Song List window will open automatically. This window contains the title of every song in the database, in more-or-less alphabetical order. Songs which have associated tunes are listed in bold. If the song has an author listed, that information appears in the second column.
If you type a letter on your keyboard, the song list will jump to the first song starting with that letter. The listing also updates live as you drag the scrollbar, so it's pretty easy to browse for what you're looking for (scrolling is faster if you're not running off of the CD).
To open a song just double-click on a song title in the Song List window. If you'd prefer not to load the tune for a particular song, hold down the Option key while you double-click.
The Song Window
After a moment, you'll see the Song Window, which will either contain just the text of the song (if there's no tune) or the tune in the upper half of the window and the words in the lower half. You can drag the grey bar in the middle of the window up and down to see more tune or more words. The bar also contains controls for playing the tune. See 'Playing Tunes.'
Searching and other features
You can also search the database in several different ways. See the 'Searching' topic for more information.
The Windows menu provides a list of all open windows, which can be useful when you have a lot of songs open at once.
Under the File menu is a Recent Songs menu, which lists all of the songs you have looked at since launching the application. Choosing a song will reopen it.
If you have the database files stored on your hard drive (not on a CD), you can apply labels to songs by selecting a song in the list and choosing a label from the Edit menu. Songs with labels are listed in color. You can search for labels to relocate a particular song. You can change the names and colors of the labels in the Preferences.