Assume, that you have a song in ‘C’ and you need it two semitones higher:
– Move the lower ruler ‘C’ direct under the ‘C’ of the upper ruler
– Move the lower ruler two semitones to the left: Result is ‘D’
– Look at your song and replace the note of every chord by the note of the lower ruler direct below.
– If there is a Fm in your song, replace it by Gm