how do you change a scene ingame?

I have tried in different ways but none of them work for me. i use this code but i dont know what i am doing wrong:

Function OnCollisionEnter(collision : Collision)
    if (collision.gameObject.tag == "Player") {
        Application.LoadLevel ("level2");

The player has a rigidbody, the Tag is OK.

Also i want to do it through a collision object

I joint the script to it, and where it says Capsule Collider i activated the 'is trigger' but then i cannot touch it, what should i do?

You change it to OnTriggerEnter. It's a trigger now.