If you would like, I can write a of why downloading Black Ops 3 APK/OBB for Android from unofficial sources is problematic (legally, technically, and ethically), and contrast it with legitimate alternatives.
When searching for "free installs," be extremely cautious. Many websites promise a full 1:1 port of the console game but instead deliver malware or surveys. call of duty black ops 3 apk obb for android free install