From the airport MTR station, take the MTR to Tsing Yi (青衣) station that is one staion away.
At Tsing Yi station, cross the platform to transfer to the Orange Line.
Alight after one station at Lai King MTR station where you will cross the platform again to transfere to the red line.
On the red line, take all the way to Prince Edwards MTR staition.
Metropark Mongkok is only less than 5 minutes walk away from Prince Edwards MTR station.
It might sounds qutie complciated but this journey will be quite easy and convenient. You might wanna look at
http://www.itu.int/WORLD2006/visitor_info/images/00001085.jpg
so that the above instruction makes more sense. Hope this information helps. Let me know if you need any more help.