Getting the game icons on the front page is an easy task to install the wad files, unfortunately not all wad files on all systems are equal as some work and some don’t so you will have to experiment installing them to see what works on your system.
Mario cube as a large selection of wad files https://mariocube.com/
There is another collection of wad files on archive.net
You can get more from the internet by searching “Wii Wad files”
Once you have the wads you want either copy them to a Fat32 USB stick or put them on the a SD card.
Simply open homebrew, and navigate to the “Yet Another wad manager” then open it.
Then press load and press button A every time it asks, all the way through until you see the files list above.
Then if you are using a USB stick, press button B and select USB drive.
Then simply select each wad file and press button A, it will then present you with an option to install or uninstall each wad.
Simply select install and let the will do its thing.
Have fun, any problems please leave a comment and i will respond.