Projectile help (shuriken, throwing knife, etc)

So Im trying to make a third person arena style game where you can fire projectiles straight forward with a maximum range and a cool-down. I am very new with Unity and I dont have any coding experience however I have been learning through (scripting) tutorials. What I have made already is a spawn point for the projectile and the actual projectile I just do not know how to make the projectile spawn on command and I don`t know how to give it velocity.
I assume it is a small script since it is only a few commands so if anybody can either give me the script or tell me how to structure it I would be more than happy.

I’ve made this script in JS for grenades, hope it will help you:

var grenades = 0;
var grenadePrefab : Rigidbody;
var grenadeSpeed = 15;

function Update () {
	if(Input.GetKeyDown("g") && grenades > 0){
		var grenade = grenadePrefab;
		grenade = Instantiate(grenadePrefab, transform.position, transform.rotation);
		grenade.velocity = transform.TransformDirection (Vector3.forward*grenadeSpeed);
		grenades -= 1;
	}
}