Apple TV 2 - do I need to downrade ?

I have Apple TV 2 with Apple TV Software 5.1.1 and OS Build version 6.01.

What should I do to get xmbc program installed on my Apple 2 t.v. ?

Do I need to downgrade both software and OS build or what ?

If so, what version to and how do I do it ?

After I install xbmc I need to get that zip file as an add on so will be able to get Iceland Films.
I know how to do that on I-pad, I-phone. Android and P.C.. But how do I do that on my Apple 2 t.v. ?

Thanks