This plugin will retune your score to any tuning of Porcupine Temperament. (But it's not really meant for "converting" your song into Porcupine Temperament. It's meant to be a tool that allows you to compose in Porcupine temperament!)
Just choose the "generator size" (around 160-165 cents for the purest intonation), or click an equal temperament preset, which simply fills in the corresponding generator size for you.
The staff is set to Porcupine temperament's 7 note scale, which has 1 large step and 6 small steps. The large step was put between G and A (makes sense I think). You can learn more about porcupine temperament in this video:
The plugin applies to selected notes, or the whole score if nothing is selected.