The video presents a full process of updating the stock (branded) Android 4.1.1 (HTC 3.14) to stock (debranded) Android 4.2.2 (HTC 4.18).
BUT it is also valid for flashing custom roms like:
What you need:
- HBOOT version 1.3x or higher
- Unlock_code.bin file from HTCDev to unlock the bootloader (http://www.htcdev.com)
- Hasoon2000's All-In-One Kit for the One X (http://forum.xda-developers.com/showthread.php?t=1604439) - for easy bootloader unlock and CWM flashing
- ZIP file with the latest rom (http://forum.xda-developers.com/showthread.php?t=1546970)
What you do is in the video, but in short:
1 - make a backup with Titanium Backup or alike
2 - unlock your bootloader
3 - flash CWM
4 - make a full nandroid backup with CWM
5 - wipe / restore factory defaults + wipe cache partition + wipe Dalvik cache: all in CWM
5 - flash ZIP from SDCARD (the actual new rom)
6 - flash boot.img for the 4.18 firmware
7 - enjoy
Credits go to Hasoon2000 for the A-I-O Kit and Mike1986 for preparing the flashable ZIP files etc.
For some very good FAQ go to: http://forum.xda-developers.com/showpost.php?p=44732947&postcount=4
For more great support visit the XDA website and forums: http://www.xda-developers.com/
Best of luck!