The Cadd9 guitar chord is one of those that sounds a lot harder to play than it actually is.

Wedge your ring and pinky fingers on top of themselves and place them as a unit on fret 3 on the thinnest strings.

Then take your index and middle to fret the other notes. If you know the “folk g” chord then you’ll do fine with this one. Just move that index and middle finger down a set of strings and keep the other fingers the same.