CODE EXAMPLE FOR CSHARP

how to look around with mouse in unity

public class CameraController : MonoBehaviour //The script should be on the camera or on the player if it is a sphere
{
	
  	Vector2 rotation = Vector2.zero;
	public float speed = 3; //the sensibility

	void Update () 
    {
		rotation.y += Input.GetAxis("Mouse X");
		rotation.x += -Input.GetAxis("Mouse Y");
		transform.eulerAngles = (Vector2)rotation * speed;
	}
}