I have a transit flight from dubai -hongkong - manila and i am a nepal citizen living in uae dubai

Riyaz, you cannot obtain the transit entry permit at the airport. You should apply for it ahead of your trip.
The required documents include copy of your passport, the application form with a passport-style photo attached, proof of your financial support, transportation arrangement, and proof of the proposed visit in the next destination after transiting in HK. After, you should submit your application to the embassy of PRC to apply for it. It the embassy deals with your application, it usually takes 4 working days. A transit entry permit costs HKD 100.