Touch jumping controle

im having some issues and dont know where to start i have touch controls that place analog sticks on the screen (iphone) these move my player i didnt make these, i need to do much the same thing but have a simple circle display on screen that when touched makes the player jump any ideas?

Try and use this script too get what u need out of it.
hope it helps.

var JumpButton: Joystick;
private var character : CharacterController;
private var velocity : Vector3;
var jumpSpeed : float = 8;
var inAirMultiplier : float = 0.25;
var cameraPivot : Transform; // The transform used for camera rotation
var rotationSpeed : Vector2 = Vector2( 80, 80 ); // Camera rotation speed for each axis

private var thisTransform : Transform;
private var cameraVelocity : Vector3;

function Update () {

}

function Jump () {

var movement = thisTransform.TransformDirection( Vector3( moveJoystick.position.x, 0, moveJoystick.position.y ) );

// Check for jump
if ( character.isGrounded )
{
if ( JumpButton.tapCount == 0 )
{
// Apply the current movement to launch velocity
velocity = character.velocity;
velocity.y = jumpSpeed;
}
}
else
{
// Apply gravity to our velocity to diminish it over time
velocity.y += Physics.gravity.y * Time.deltaTime;

// Adjust additional movement while in-air
movement.x *= inAirMultiplier;
movement.z *= inAirMultiplier;
}

movement += velocity;
movement += Physics.gravity;
movement *= Time.deltaTime;
}