STEP 1: Use PwnageTool to jailbreak your Apple TV, by following the step by step guide posted here.
STEP 2: Once jailbroken, open Terminal and SSH into your Apple TV2, the default password is "alpine"
STEP 3: Type "passwd" and enter a new password (if you haven't already)
STEP 4: Type: echo "deb http://apt.awkwardtv.org ./" > /etc/apt/sources.list.d/awkwardtv.list
STEP 5: Type: apt-get update
STEP 6: Type: apt-get install com.nito.nitoTV
STEP 7: Type: killall Lowtide
That's it, now you can enjoy your first ever jailbroken app installed on your Apple TV 2G. Let's wait for more to come!