Explosion on contact?

I am in an orginization called TSA(technolegy student assocoiation)I need to find a script that makes an explosion when it makes contact with the firt person controller?

You don't give much info, but here's a pseudo-code, in JS:

var theExplosion:GameObject;

function OnCollisionEnter(coll:Collision){
    if(!coll.gameObject.GetComponent(CharacterController)){ return; }
    Instantiate(theExplosion,transform.position,Quaternion.identity);
}

This is a pretty basic example but it should do what you need. Just drag the explosion prefab in the Inspector.