Just flash it with CWM, see the tutorial below for CWM.
Samsung Galaxy Y must be rooted.
1. Download and save the cwm.zip and sgy_unlock.zip in sdcard
2. Reboot to stock recovery (turn off phone then press home+power+volume up)
3. Search option Apply update from sdcard
4. Look for CWM then select and install it from sdcard.
5. Select sgy_unlock.zip.
7. Then reboot.
Please remember what I said use it at your own risk! Thank You!