If its a Note 3 N9005 then you just download the OS version you want from Sammobile.Com and flash with Odin.
You can't go back, to JB if you don't like KK though as the bootloader won't allow it.
You will need to re-root it afterwards and Knox will be void.
If you used URDLV(sorry, bloody autocorrect) and Knox is still not tripped then look in the mobile Odin thread to upgrade without loosing root... You do need to flash a KK bootloader through PC Odin separately though.
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