To transpose, just use a circle of fifths. Above, the song is in C major. So it is represented by I. To the left of it is the IV which is F major. The V is G7. The other positions ii (D), iii (E), vi (A) and vii (B) are all minor chords (that's why they are in lower case).
Now suppose you want to change the key of this song to D. Then D major becomes I, G major becomes IV, A7 becomes V, E minor becomes ii and so on.
Just remember that the V position is really a V7, that is, a major triad with a minor 7th. You need that to resolve back to I or to shift keys for those songs that shift key.