This is a Custom ROM and not an official update.
Make sure that the battery of device has a minimum charge of 60%.
Enable “USB debugging” on your device by going to Settings >> Developer options >> Enable USB debugging.
Install ClockworkMod Recovery on Galaxy S4 M919.
Connect your device with computer via USB cable.
opy/paste the downloaded Android 6.0.1 ROM zip and Google Apps zip files to your SDcard root folder.
Switch off your device.
Enter Recovery. Hold power button and volume down button and enter recovery.
Select “wipe data/factory reset”, wipe cache partition” and in Advanced select “Wipe Dalvik Cache”.
Select “install zip from sdcard” and then select “choose zip from sdcard”. Navigate to “Android 6.0.1 ROM” file which you have downloaded and confirm to “install”. Wait till it gets installed.
Repeat the procedure to install Google apps by selecting “choose zip from sdcard” and then select “Gapps.zip” and install.