I need help with collisions between my player and gameobjects

This will see like a very newbie question I understand that but I need help. I am trying to make a simple 2d platformer. I have already made my player and my platforms but I am having trouble with my collisions. I just want my player to be able to run into say a cube that I place in its way and push it or knock it back anything. As it is my player floats off the ground and I can not for the life of me get it to touch anything. So I can't get a on-collision scene change to work or anything that involves the player touching anything. My player is just a simple sphere with the unity platformer controller on him and a rigidbody with more mass than the objects I attempt to collide with.

First, the object you want to push or knock back has to be tagged correctly and has to have a rigidbody.

You can use the function "OnCollisionEnter (collision : Collision)". Put a if statement checking for the right tag. Then find the direction you want to push the object by creating a variable that creates a normalized vector3 to the object to get the direction, then use

collision.transform.rigidbody.AddForce(yourDirection*yourForce);

If you need an exact script, comment on this post and tell me and I'll edit it.

This method adds force anytime you touch the object, even from above or below.

I hope this helps. :)

EDIT: The actual script (Tested):

var yourForce : float = 10.0;

//Detects collision
function OnCollisionEnter (theObject : Collision) {
    //checks the tag to see if you got the right object
    if(theObject.gameObject.tag == "Moveable"){
        //create the direction vector3
        var direction = (transform.position - theObject.gameObject.transform.position);
        //I am not sure you have to do this, but I did it just in case
        direction = direction.normalized;
        //add force
        theObject.gameObject.transform.rigidbody.AddForce(direction*yourForce);
    }
}

Please ask another question for the changing scenes part because they aren't very closely related. Well, except that you will still have to use OnCollisionEnter.

SECOND EDIT: Just a little help on the changing scenes part. Using a version of the script above, (you must first get the build settings right before once you have finished your scene) then use

Application.LoadLevel(theLevelNumber);

Once again, hope this was helpful.