You'll need a way of booting Gamecube homebrew. Some of these ways include:
1.) SD Media Launcher (by
Datel)
2.) Modchip
3.) Phantasy Star Online Episodes I & II (NOT plus) along with a BBA and Cat5e Cable.
4.) Old Action Replay (GCN) + SD Gecko
Now, I recommend the SD Media Launcher. Options 3 and 4 are not only expensive to get; but can be a HUGE pain to find nowadays. I doubt you want to mod your Wii/Gamecube either.
The SDML (
SD Media
Launcher) will probably cost you around ~$30 USD (with shipping). It can be found on
codejunkies. I assume you don't need a SD Card, so don't buy the bundle packages (they cost more). I got mine within a week of ordering it.
EDIT: SDML also works on Wiis with 3.2 and below firmwares. I'm unsure if it works on 3.3.