just put the mod in the content folder (wiiu/games/smash/content) make sure you have smash updated. it should work depending if the mod pack is already packed but if it isn't then you would need to set up sm4shexplorer
you can check if any of the sd cards works with smash (take a screen shot) or mii maker (save a QR code). If none of your sd cards work with those then you might have a broken reader.