When doing this on a DAW I go by spaces between notes. Place a note then go two spaces up, place another, then 3 spaces up, add one more; there's your minor chord. You can continue and add another one 2 spaces up to create a fuller sound (which I always do or I add even more). You could also add voicing where you take one or more of the notes in the chord and copy+paste it an octave up or down. Edit: This is for other people. Ed knows everything lol.
It’s because he is referring to the 5th note of the key of D (a D major scale consists of D E F# G A B C# and back to D), so the 5th note in the key of D is A. Since the key of D doesn’t include every note on the piano, to actually get to A from D is 7 notes (D -> D# E F F# G G# and then A). Hope that helps!
