Custom recovery is a enhanced mode of stock recovery which will make you able to perform the tasks which are not possible through stock recovery like installing the zip files, taking nandroid back ups, mounting unmounting the data/system/cache/USB storage
To get the CWM recovery for your android device check out this link get the
zip file for your device and store it on your sdcard and follow the steps below
- Once you have the CWM recovery for your device stored on your SD card switch off your phone and reboot into recovery mode.
- To get your phone in recovery mode use the key combination (Power+ Home+ Volume Rocker)
- In recovery mode select the option install zip from sdcard and browse for the zip file using volume rocker and select the file using home key.
- Once the installation is complete, select the option reboot system and reboot the device
- Now you have changed the stock recovery to CWM recovery.