To remove the top "white" cover, you first have to remove the front (black, trapezoidal) cover (the one with the stuck-on metallic "Kenwood Chef" label); this is a user operation, to fit the mincer attachment I believe, but if this has never been done, it may be very stiff and sticky. Pull the square-ish red knob out to the side: it should move about an inch or so, but may be reluctant to move that far at first; the black cover can then be pulled away from the machine (wiggle it - it has a central round plug jammed into a greasy round hole).
Paul Singleton, August 2023