#go to cwm recovery by pressing (power button + volume up + Home button)
#select wipe / data factory reset >>> then select yes.
#Select Wipe cache partition >>> then select yes.
#then select mounts and storage> format / system> yes format
#then select advanced option >>> then wipe dalvic cache and wipe battery stat.
#then Return to the main menu again.
#select Install from sd card> install zip from SD card> select -Custom Rom> yes.
#then a process will occur.
#wait untill it finished.
#After Finishing rom installation install FIX.ZIP
#then reboot your Primo EF2

Procedure for Flashing a custom rom via TWRP recovery 

# Power off your phone.
# Turn your phone on in recovery mode (by pressing VOLUME UP + POWER buttons).
# Go to TWRP {Also known as Recovery Mode. }
# GO> WIPE> ADVANCED WIPE> SELECT - DALVIC CACHE, CACHE, DATA, ANDROID SECURE, SYSTEM AND THEN SWIPE TO WIPE
# THEN A PROCESS WILL START AND WAIT UNTILL IT FINISHED.
# THEN SELECT- BACK AND RETURN TO MAIN PAGE.
# NOW THE FINAL PART- SELECT - INSTALL> SEARCH YOUR ROM
# AND THEN SWIPE TO CONFIRM FLASH.
# WAIT UNTILL IT FINISHED.
#After Finishing rom installation install FIX.ZIP
# REBOOT YOUR PHONE / SYSTEM REBOOT ...