NOTE: 

Make sure the phone is rooted before trying this.

Otherwise please follow this video to root your Galaxy Note 3.

In this video we’ll go through and install clockworkmod recovery and then install google apps which will allow us to access google play store.

This will definitely trip knox so no going back after this.

Please note this video is only for Jelly Bean (Android 4.3) and is most likely now outdated. If you are running KitKat (Android 4.4) please watch this video on installing TWRP.

Links:

Gapps TKruzze

https://forum.xda-developers.com/paranoid-android/general/5-1-x-5-0-x-4-4-x-pa-gapps-mirror-t3069879

ClockWorkMod (CWM) Recovery

https://galaxynote3root.com/clockworkmodtwrp-recoveries/