I am Nepalese residents, how to get tourist visa for HK?

First, prepare the relevant documents including the application form, a passport-style photo, copy of your passport, proof of your financial support, proof of transportation and accommodation arrangement, and your travel plan.
Second, post your application to HK immigration department to apply for the tourist entry permit. Here is the postal address:
Receipt and Despatch Sub-unit
HK Immigration Department
2/F, Immigration Tower
7 Gloucester Road
Wan Chai, HK
Actually, I haven’t heard that Nepal citizens cannot visit HK. As long as you have valid entry permit for HK, I think you can go there for a visit.