If you're gonna do it before hiring them anyway just edit them with
Morgh's. It's recommended that you start a new game if you edit any NPC with Morgh's especially for stats, since the changes won't show up until you start a new game.
This guide is for because you already hired them and can't change their stats with Morgh's (stats get saved in a save game so that if they level up, you can edit their stats in-game).
If you have already started a game and don't want to restart just because of using Morgh's, but you haven't hired the companion yet, then there is no real point to wanting to change the companion because the companion's stats are meaningless until you hire them.
Basically either you use this guide after you hire them, or if you're gonna start a new game anyway just use Morgh's.