First things first, you will need:
USB keyboard to connect to OUYA (Preferably wired)
USB micro connection to PC
A PC (duh)
Next, you’ll need to setup ADB (Android Debug Bridge). Basically you need to install a specific driver on your PC so it can communicate with the OUYA directly.
S-Config’s How to Install Guide Here:
https://forum.xda-developers.com/showthread.php?t=2344097
Once you have that driver installed, you’ll need to download the most recent firmware and sideload it through the ADB you just set up.
S-Config’s How to Update Firmware Guide Here:
https://www.s-config.com/section-5-restoring-you-ouya-firmware/
Then you’ll want to make sure to install the new server, guide here:
https://ouya.world/t/how-to-bypass-account-login-firmware-update-page/15