The best way is to take the subway Ma 'anshan Line (Tai Wai direction) from Ma 'anshan Station in Newport City, then transfer to east rail line No.2 Station (Hung Hom direction) and get off at Mong Kok East.
Another way is to take the subway Ma 'anshan Line (Tai Wai direction) from Ma 'anshan Station in Newport City, then turn from Tai Wai to east rail line Station Road 1 (Hung Hom direction), then turn to Kwun Tong Line (Yau Ma Tei direction) and get off at Mong Kok.
I hope the above answers can help you.