GarageBand on my Mac

Hi all,

I recently purchased a Mac, and would like to use GarageBand to compose music. I would like to know if there are any Tutorials on how someone can use GarageBand with voiceover? More specifically, I would like to know how to Record different parts of a song such as the chorus, and verses, as well as Duplicating a region of the song to make it longer, and Recording it and external instruments. Please let me know the resources that might help