How to change a vanity bulb in a Vw Golf MK4?

I've been googling for days now and I can't find a way in which to change the vanity light (that's the little light that comes on when you drop down the sun visor in a car) in a VW Golf MK4. Anyone?|||The casing should snap off and on. Get a flat edged item to work as a lever then change it snap back on