Steps:
1. Download radio-cm-10-i9100-LQ6-signed.zip (from CM10 XDA thread) and copy to internal sdcard.
2. Reboot to CWM Recovery.
3. Choose "install zip from sdcard".
4. Choose "choose zip from internal sdcard".
5. Choose "radio-cm-10-i9100-LQ6-signed.zip" and confirm.