Help with itunes apps

Hello,

I have an ipod that belongs to a friend. He had downloaded all his apps from his desktop. When i connect it to my itunes library, i am able to manage music,videos,photos..etc BUT i am no able to manage the apps. I have downloaded some apps on my desktop and i cant even put it into the ipod.

Can anybody tell me how can i solve this problem? It's really annoying.