Can`t install apps on iPod Touch

hi

I can not install my apps on the iPod. I have downloaded them, I have them on my computer.
but if I want to install them, iTunes says, that i havn`t activated them.
in the menubar under "store" you can activate it. but if I do this, it says that I have activated 1 computer inclusiv this one.

when I try to install the apps again on my iPod,coming the same like before.

I Hope Anyone Can Help Me, I Don`t Know What To Do!


Your sincerely
Marvin