Hi am from gambia .west africa I want to apply for student visa to HK. How would I do that.

Alagie, you should first find school to enroll you and then you can apply for the student entry permit.
You need to prepare the following documents:
1. The application form attached with a passport-style photo
2. Copy of your passport
3. The admission letter from the school in HK
4. Proof of your financial support
And then post your application to HK immigration department to apply for it. The postal address:
Receipt and Despatch Sub-Unit
HK Immigration Department
2/F, Immigration Tower
7 Gloucester Road
Wan Chai, HK