To configure the FS3 Combat Skills:
The combat rules require you to determine which abilities are used for the following rolls:
composure_skill(default = Composure) - Used for knockout rolls and stress resistance.
recovery_skill(default = Brawn) - Used to determine if someone gets a bonus healing point during the daily healing roll.
treat_skill(default = Medicine) - Used for the treat commands to provide immediate assistance to injuries.
healing_skill(default = Medicine) - Used to determine how many patients a doctor can heal at once, and whether those people get a bonus healing point during the daily healing roll.
initiative_skill(default = Alertness) - Used to determine who goes first in a combat turn.
default_defense_skill(default = Reflexes) - Used for defense rolls outside of melee and vehicle combat. Melee combat uses the defender’s melee weapon skill, and vehicle combat uses their piloting skill. You can override this for a specific combatant type. See Combatant Types Config.
strength_skill(default = Brawn) - Used for augmenting melee weapon damage.
Although they're named "skills", you can use attributes instead. Most of them are skill-based, but things like strength and recovery don't really have any _skill_ involved so they use raw attributes. Just be aware that if they're only rolling an attribute they've got fewer dice on average.