Sync
One way to import a large amount of existing songs, is via the sync method. This method searches a local hard disk for any songs which have not been added.
First click Sync from the maintenance menu:

Next fill in the path to your music collection:

Click sync and wait for the results to pop up:

Currently you can only add a single artist to a song when syncing. When your happy with the name of the artist and the name of the song, you simple click save and the song is inserted in the database:
First click Sync from the maintenance menu:

Next fill in the path to your music collection:

Click sync and wait for the results to pop up:

Currently you can only add a single artist to a song when syncing. When your happy with the name of the artist and the name of the song, you simple click save and the song is inserted in the database: