It has many great features. First let us understand what is CM. CM stands for Cyanogenmod. It is an open source project, so can make any changes. The sourcecode of CM is available at Github.
Your Device should be Rooted.
Battery should be more than 70%
CWM recovery installed
Backup of your data
Drivers of redmi 2 on PC
and lots more
Step 1: Download CM12 ROM and Gapps zip file and then transfer it to your phones SD card via PC
Step 2: Reboot into recovery mode
Step 3: “Wipe data factory reset”. After that go yo advanced settings and clean “Cache” and “Dalvik cache”
Step 4: Go to main menu and select “install zip from sd card”
Step 5: After installation reboot the phone. It will take some time to Switch ON the mobile.
That’s it. You are done. Now enjoy Lollipop taste !!!
Note: Rooting will void the warranty and we are not responsible for bricked devices and sd cards.
Source: XDA and MIUI forums