To download, first download and extract "SpellSchools.zip". Inside you will find "SpellSchools.dll"

Then, in HDT click options in the top right corner --> plugins (on the left side) --> plugins folder on the bottom. Insert "SpellSchools.dll" here.

Then, restart HDT and navigate back to the plugin settings. Enable the new "Spell School Tracking 1.00" plugin.

Now you are done! If you ever want to disable the plugin, simply disable it in the plugin settings.