Im still confused on how exactly you tune ur guitar down a half step. After you go to the 4th fret on the low E string do you go back to the 5th fret to tune the rest of them just like a normal tuning? And could you explain how exactly you drop d tune and double drop d tune.

i can`t help you with "half step tuning or double d" ... but drop d is no problem... usaly to tune your 6th string (E) you put your finger on the 5th freet... but to tune to D, just put the finger on the 12th freet instead... now, tune down the string in that position until it sounds exactly like the 4th string (D)... then you are done!
My advice is that you buy an "digitaltuner" or something if you are still not comfortable with tuning.