if you have a 7 string you dont really need to drop the E to D...
ok look at your tuner... turn the low E's tuning peg LOWER untill the E turns to D... then you are in drop D, standerd with the low E changed to a lower D note.

A full explanation of drop D would be:
drop D is basically the easy way out of tuning to 1 step down from standerd, instead of tuning ALL the string you just tune the low E string to D and play a bar chord on the 5th and 6th strings instead of a full power chord on the same strings. its faster and easyer IMO than tuning all the strings and using power chords.

and to explain sharps and flats:
a FLAT note is a note half a step down (ie: E to Eb)(Eb meaning E flat)
a sharp note is the oposite, a note a half step higher (E to E#) (E# meaning E sharp)
some notes mean the same thing, if you take a low note and make it sharp, or if you make a note 1 step higher and make it flat,its the same thing (ie: D# and Eb are the same note)

if all this is confusing, get a teacher or a pro to explain it.

this is my biggest post ever

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