My device is xperia p with cwm v18.104.22.168
- Boot to recovery,
- Connect your flash drive (if it doesn't mount automatically go to Mounts and Storage and select Mount USB storage)
- Then go to Backup and Restore option and select backup to /storage/usbdisk (which is your flash drive)
That's it.Wait till the backup ends and reboot your device.
If you want to restore the backup follow the same steps but in step 3 select:
- restore from /storage/usbdisk or
- advanced restore from /storage/usbdisk