A capability is a minor thing a pokemon has to offer, like firestarter. It means that a pokemon can start fires without using a formal move. Other examples of capabilites are glow, which allows the pokemon to act as a light source, and tracker, which allows them to... track.
You have listed on Spike's sheet:
Basic Abilities: Blaze / Flash Fire / Intimidate
High Abilities: Justified
You don't get all of these, you have to pick one of the first ones. At level 40, you get to pick another one, with which you can pick the high ability as well. Flash Fire is the best one, take it.
Also, you didn't specify a gender for your growlithe. I recommend female.
Reviewing, you did indeed specify a gender. I missed it as it wasn't in a formal spot on the sheet.