I am new to the idea of a capo. When a tab says place the capo on fret 3 and wants you to play a note on the first fret you play it on the first fret to the right of the capo don't you. Could some one tell me how exactly it adjusts your key for example D maj. Thanks!
Capo is just simulating the nut moving forward. Capo at first fret is F, second fret F#, 3rd fret G, and so on, when in standard tuning. You can't play a note behind the capo because you'll get no sound.