1. Firstly, Download Mod APK file.
2. Install Mod apk. (Don’t open it after installation)
3.Download Obb file. Sometimes only Main Obb file and sometimes both Main obb file and patch obb file.
4. Create a new folder named in the /SDCARD/Android/obb/
5. copy the Obb files to /SDCARD/Android/obb/
More instruction of XAPK installing: Here