Navigate to your Android's internal storage: Android > data > com.rockstargames.gtasa .

, though these may require special permissions to access the "Data" folder. Important Safety Note:

Delete the current version of San Andreas from your phone. A clean slate prevents conflicts.

Using ZArchiver, navigate to Android/obb/com.rockstargames.gtasa/ . Place the main.8.com.rockstargames.gtasa.obb file here.