What are you trying to install..? Tell me the whole name of the wad file, please. And You shouldn't mess around too much with wad files! It's a very easy way to brick your Wii if you don't know what your doing.. But I have told you this before! ^^
Wii shop Channel v18.rar
Here's a link to the ShopChannel update. Put these (.wad) files in your WAD directory on your SD card, and install them with Wad Manager version 1.5. Use IOS249 when installing.