hello sir im a nepali citizen working in UAE but planning to visit hk for 10days so how may I start.

You go there for sightseeing purpose, right? If yes, the first thing is to prepare the required documents including copy of your passport, the application form, a passport-sized color photo taken recently, proof of your financial support, transportation arrangement, hotel booking record, and your travel itinerary to HK. And then post your application to HK immigration department to apply for it. Here is the postal address:
Receipt and Despatch Sub-unit
HK Immigration Department
2/F, Immigration Tower
7 Gloucester Road
Wan Chai, HK