Please read up on CWM recovery HERE.
This needs CWM to be installed. Read HERE
BACKING UP/RESTORING ROMs:
Now that you have CWM installed, these next steps are really easy. Please follow the instructions carefully or you will screw up your system.
Backing up your system through your CWM creates a nandroid image of the android system that CWM can read. This nandroid image can help you get back to your old android system if need be.
This is the first thing you should do when you install CWM.
- Boot into CWM
- Select “Backup and Restore”
- Choose “Backup”/”Restore”, depending on the operation. The operation will start.
- Wait for it to finish and reboot.
- The file will be located in “clockworkmod” folder in your external SD card. I suggest leaving the file here, as this is CWM’s default directory and it reads all backups from here.