The Project: M codeset is private, and the only people who have it are the P:M developers. So, you can't actually use the txt file.
However, you can add-on existing codes to the Project: M gct. Use this: http://forums.kc-mm.com/Gallery/BrawlView.php?Number=20040
. It let's you append codes to a gct so you can add-on your own stuff to the P:M set.