Here's some quick instructions:
1) Root your device with Kingo Android Root
. Make sure your phone is on debugging mode (about phone, tap the build name several times, it will activate developer menu)
2) Install Philz Recovery
through Odin in download mode (Vol down+ Home button+ Power): [It seems to be less error with Philz Recovery on Knox affected Mega in my case, so I suggest you to use this one instead.]
3)Download the latest CM11 version
. Go in ROM folder, then CM11, and choose the latest version.
5) Put the last two files on your internal SDcard.
6) Reboot to recovery (Vol up + Home button + Power).
7) Wipe data/cache.
8) Install CM11.
9) Install GAPPS.
That's it, enjoy!