Advice for Binaral Beats?

i am trying to lucid dream and astral project. i have at least 3-4 lucid dreams a month, and once i had an astral projection. but then i heard of binaural beats. i downladed some from itunes, made by Erick Brown. i got four of them. Alpha, Beta, Theta, and Delta. i am just wondering when i use which one? any good advice?