This is an easy one.
1. Look at the Lemonade : All-in-One directions. Download the script and the tarbal.
2. Paste the script in the Custom Firewall window as usual. Save.
3. Shut down your router, remove the USB drive, and mount the USB drive on your computer. Delete the opt/ folder on it. (If you have any special customizations, you may want to copy opt/ to your desktop, so that you can copy your special files back to the new opt/).
4. Untar the new lemonade tarball, and drag its opt/ to your USB drive. Unmount your USB drive, remove it, plug it back into your router, and power up your router.