I'd say grab a front corner in both hands and try to lift it up a bit by rocking it up and down, repeat this on the opposite front corner, then do the same on the rear, by now you should have eased up all four fixing points, although some may now be back down, so now try raising the front back up, look underneath before you lift it too high, and remove the small pipe at the filter housing end. This cover/filter assembly is secured by 4-off engine mounted wasted pegs that get rubber dounut sort of fixings pushed down over them