(just beginning piano so forgive my naivete) How do I know what keys make up these chords?

Question

I'd like to figure out how to play this song but I don't know what keys make up all the Dm's and C's and what not... how do you figure that out?

here is what i'm trying to decode:
http://eltonchords.com/chord_library/harmony.txt

Answer 1

The site below might help you out. It shows you how to make the cords.

Answer 2

Dm means D minor. Press the keys d,f, and a at the same time for the Dm chord. For C chord press c,e,and g at the same time.