Steps:
1. Download radio-cm-9-LPS-galaxys2-signed.zip and copy to internal sdcard.
2. Reboot to CWM Recovery (v6.0.1.2).
3. Choose "backup and restore".
4. Choose "backup to internal sdcard".
5. Go back to the main menu.
6. Choose "install zip from sdcard".
7. Choose "choose zip from internal sdcard".
8. Choose "radio-cm-9-LPS-galaxys2-signed.zip" and confirm.
9. Reboot.