Do you want to know what to do in Word, or PowerPoint? This isn't the Word
newsgroup, but in Word you'll want to open your template, which is Normal.dot
(File > Open > Files of type: Document Templates (*.dot). Set the font size and
then do a File > Save as > Document Template(*.dot) and keep the name as Normal.
Close Word and then open Word and you'll see the font set to your liking.