Well, find a Video on How To see Games on tne WaraWara Plaza on YouTube, Hope you can have revival of WaraWara Plaza! :D

Press L, Dpad Down and select all at once on the home menu. Select inkay and choose BOSS. Hold A until it says done then press home. Once it resets itself you need to restart your console and it will work.

In addition to what alex said, make sure you have inkay downloaded from the github(not the homebrew shop) and installed on the correct place on your sd card