Step One
Create a folder on your desktop called Pwnage.

Download the Apple TV 2 iOS 5.2 firmware and Sn0wBreeze from here and place them into the Pwnage folder.

Step Two
Extract the Sn0wBreeze archive to the same Pwnage folder.

Step Three
Launch the Sn0wBreeze application from the folder we just extracted.

Step Four
Click the arrow at the bottom right to begin.

Step Five
Click the Browse for an IPSW button.

Step Six
Navigate to the Pwnage folder on your desktop, select the ipsw we just downloaded, and click Open.

Step Seven
Once your device is determined, click the arrow at the bottom right to continue.

Step Eight
Click to select Simple Mode.

Step Nine
You will be asked to set the root partition size. You can leave the default and click the arrow at the bottom right to continue.

Step Ten
Your custom IPSW will now be generated.

Step Eleven
Once the custom IPSW creation is complete you will be warned that after setting up your Apple TV the screen may be blank for 60 seconds. Click the OK button.

Step Twelve
You will then be asked if you want to donate to the evad3rs for the untether. Click Yes if you wish to donate immediately or No if you do not want to donate at this time.

Step Thirteen
You'll then be informed that custom IPSW has been placed on your desktop. Click the large OK button to begin instructions on how to put your device into a restorable state.

Step Fourteen
Plug your Apple TV 2 into the computer using a micro-USB cable and click Start

Step Fifteen
In five seconds you will need to press and hold both the Menu and Play/Pause buttons on your Apple TV's remote for 7 seconds then release.

Step Sixteen
Once you've done this, iREB will run placing your device into a Pwned DFU state and iTunes will be ready for your to restore to your custom IPSW.

Step Seventeen:
Hold down the Shift key and click the Restore Apple TV... button.

Step Eighteen:
Navigate to the desktop, select the custom IPSW that Sn0wBreeze placed there, and click the Open button.

Step Nineteen:
iTunes will prompt you to confirm the restore. Click the Restore button.

Step Twenty:
Once your Apple TV has restored successfully you will be ready to use your newly jailbroken device.