I have chinese visa , I am from nepal. How can I apply for Macao?

Mainland PRC entry won’t work to go there.
If you go there for tourism purpose, you should apply for a visit entry permit and first prepare the required materials including the application form with a passport-style photo glued, copy of your passport, your entry permit to mainland PRC, proof of your financial support, hotel reservation and round trip tickets as well as travel itinerary. After, submit your application to the consulate general of PRC to apply for it if you are in Nepal; but if you are in mainland PRC now, you should submit the application to the Beijing Office of Macau SAR to apply for it.