- If using the controller wirelessly, make sure to connect it to your SteamOS system using a micro-USB cable; if the controller was powered on, you might need to disconnect and reconnect the USB cable once to switch to wired operation
- Sign in to your Steam account
- Navigate to Settings -> System using the analog stick and press the "Check for SteamOS updates" button
- Wait until the update icon stops spinning
- Navigate back to the home screen with the B button
- Find the SteamOS update message in the Inbox envelope, and apply the update
Please note: Restarting your Steam Machine does not automatically apply updates.