How to edit the looking on the FP controller?

As you know, the default Unity FPS controller uses the mouse to look around and aim the character, and the keys to strafe and move. Instead, I would like the forward and backwards to stay the same, but the left and right arrows to rotate the character, freeing up the mouse for interaction. How would I go about this?

You can edit the Script. Replace the original Update function with

void Update ()
        transform.Rotate(0, Input.GetAxis("Horizontal") * sensitivityX, 0);

By doing this you read the Input nor from the Mouse but instead from the Axis Horizontal which should map to the right and left key.