A WAD file is bundled channel you install on your hacked Nintendo Wii. It may contain a custom IOS, virtual console game or an application to expand capabilities, such as running your Wii to play movies or use as an FTP server. In order to install a WAD, whether your Nintendo Wii is NTSC or PAL, you need to have a WAD Installer to run through the HomeBrew channel.
Download WAD Manager.
Double-click the archive and extract the contents to the root drive of your SD card.
Double-click "Computer," then double-click the SD card. Right-click and select "New Folder." Create the folder and name it WAD.
Paste the WAD or WADs you downloaded into that folder.
Insert your SD card into the Nintendo Wii and launch WAD Manager through HomeBrew.
Choose the IOS to use to install the WAD. Typically 249, the default, works for nearly any WAD. Select where the WAD is located on your card, then press "A" to install. Exit WAD Manager to complete the process.
You must have a hacked Wii with HomeBrew on it in order to install WADs.
You may void your warranty by making any modifications to the software on your Wii. Only use WADs for games you already purchased.