You should be able to find them like in regular Pokemon games, go around dungeons and eventually a Pokemon will be shiny. You can also use these Pal passwords to get some shiny Pokemon.
Also be aware that only these Pokemon can be shiny in the WiiWare games.
This is a video I found of someone getting a shiny: https://www.youtube.com/watch?v=LY0tOb4WCI8
Hope this helps
