skins

Having seen such nice skins on the web i downloaded some instead of making my own( I'm lazy when it comes to learning)I've taken some skins off of other games and they work when put on a custom unit,but those i download don't show up on the editor or in the game even after several loads,i read in the forum about converting files so downloading the converter i had a go but they resister as unknown file format.some of the downloads seem to be portraits only(as in icons not skins.)
what do i do to get these working