Evolution doesn't occur on this game. It's basically a D/P Battle Tower emulator for the Wii. There's really nothing to do except battle w/o gaining XP, in fact it just copies your Pokemon to the Wii instead of trading/storing them to it like previous games.
Wait, I thought you could level up your pokemon on this game(not on Wi-FI of course).
I'm preatty sure that was said several times before.