Seting Fire Up as a attack

Questions & Answers
1

What do I have to do to take a fire particle system and make it able to be fired by the player and destroy objects?

2

a particle system can be attached to any GameObject… to be able to fire said game object, use Instantiate:

http://unity3d.com/support/documentation/ScriptReference/Object.Instantiate.html

To destroy the object hit, you would use OnCollisionEnter or OnTriggerEnter:

http://unity3d.com/support/documentation/ScriptReference/Collider.OnTriggerEnter.html

I suggest looking over the getting started tutorials, probably would answer some of your questions