This would be a maneuver, adding a "fire arrow" aspect. The person with the arrow can then Tag the aspect for a +2 bonus on the roll. By RAW, you can't add multiple aspects to tag to an arrow, but I suppose a GM might let you do that, or to spread them out among different arrows (so a more powerful wizard could make a "Fire Arrow" that was "Extremely Hot"). Thaumaturgy can do multiple aspects, but it looks like evocation can't as I read things (it could make it so that you can spend fate points to invoke the aspect after it has been tagged though).