You don't need software to package things, just put it in Add-Ons and see if it works.
You're stupid.
You don't need any downloaded software, as all you need does come with Windows.
You have to have the print (which I believe is 256x256?) and a thumbs folder with a smaller version of the image (100x100?) in it.
I'm probably thinking of decals, but I think they're nearly the same, except for the required .cs file and all.