1)Through TWRP Recovery:
Copy your rom.zip(the ROM file that you have downloaded and
want to install) on external sd card/internal SD card
**Install twrp
recovery through mobile uncle tool(If already installed,leave this step)
**Reboot into
recovery(press and hold Volume up +power button)
Taking Backup of current ROM:
**Backup->check
system,data,boot,recovery,cache,uboot and nvram ->swipe right to backup
(If you don't want to take backup of your current ROM,leave this step)
**Select wipe
**Select
Cache->swipe right to wipe
**Select Dalvik
cache ->swipe right to wipe
**Select Factory
Reset->swipe right to wipe
**Select
System->swipe right to wipe
**Select Install
**Scroll up/down and
select the desired rom.zip to install->swipe right to install
**Reboot-> system
2)Through CWM:
Copy your rom.zip(the ROM file that you have downloaded and
want to install) on external SD card/internal SD card
**Install a custom
recovery through mobile uncle tool(CWM)(If already installed,leave this step)
**On your phone the
USB debugging option must be enabled: “Settings -> Developer Options -> USB debugging->on”.
**reboot your phone
into recovery mode(press and hold Volume up +power button)
**Backup first
**After backup
complete select “wipe data factory
reset”
**Select “wipe cache partition”
**Select advanced menu and do “wipe dalvick cache”
**return to recovery
main menu
**choose zip from SD
card
**choose the update file and flash the same
**Done