key changes and stuff

ok...there is this song im wanting to play and it says its in the key of D......would i put a capo on a certain fret?

Well, if you wan't to play it in the key of D and the song is in the key of D you don't have to do anything. But if you want to play it in the key of E you've gotta use the capo.. Or what was it you asked for? I dont understand the question

If a song is in the key of D, you can use a capo to play it, but it would be quite pointless.

You can play in D with the 3 major chords: D, G, A. Most likely the song you want to play will be a 1,4,5 progression, throwing in a Bm, F#m, or Em somewhere.

However, if you want to play it with the chords G, C, and D, (Key of G), you can put a capo on the 7th fret, and play those 3 chords. That will be in the key of D, using the shapes G, C, and D.

Though... i don't think that's what you're looking for.