how to download application in apple tv

yesterday i buy apple t'v and my friend he has the old update he can download application and i can't download because i don't now how and i go to the shop i buy it from he tolled i don't now ask apple support how to download application from apple t'v. and i want you to teach me how to download application in apple tv and he had shahid.net and i want to download it pleas teach me how to download