No particular rules. The easiest way to do it is just to give them a name and personality, and presume they make any dice rolls they would need to make. If you want them to be a little more dynamic to the characters in social situations, figure out about what Tier they would be, figure out what skills they would be likely to have, and give them +3/Tier on all their rolls (or +4/Tier for Tier 4/5).
If you want them to be active combat participants, same thing. No special abilities, no special tricks. If necessary, give them a spell or two (for instance, if they need a healer, give them Diminish Fatigue and one other spell from the Corpus tradition).
Just a quick and dirty support NPC. Remember, above all, to give them an actual personality rather than ‘standard meatshield 2’.
