How To Install Master Presets On Logic Pro X & GarageBand
Before watching this video please open up Logic or GarageBand and in the top left menu bar click Track > Show Output Track (Logic) Show Master Track (GarageBand)
Master presets need placed in this folder: /Users/*yourusername/Music/Audio Music Apps/Patches/Output
Next select the master track and continue to watch the video below. Make sure to apply the mastering preset on the master track, not a regular audio track.
If you can't find your "Music" folder, click anywhere on your desktop and press Command + Shift + H to bring up your Home folder and the Music folder should be here.