do you want the KNOX boot loader with Mk3 or just MK3 itself?
FULL MK3 with KNOX:
Odin to MD4 stock here
The take the update that you'll be notified of.
To run basically stock MK3 w/o KNOX:
Flash this stock MK3 rom from CNexus here
Be sure to follow the directions exactly.
Hope that helps
Sprint Samsung Galaxy Note 3 32GB - Still Stock O_o