how to i being to make force being push up all time?
If you want a constant force in some direction, add the component ConstantForce and define the force vector - something like this:
constantForce.force = 5 * Vector3.up; // apply constant force 5 upwards
To add a ConstantForce, select the object (must have a rigidbody) and click menu option Component/Physics/ConstantForce.