If you want to play online via services like Wiimmfi , you use a NAND backup from a real console.
The emulation community is moving toward preservation and legality. Search engines are cracking down on "ROM sites," and major emulators are removing features that facilitate piracy. wii nand download dolphin
Dolphin will download and install the official system files . If you want to play online via services
On a modded Wii, use BootMii to create a backup. This generates nand.bin and keys.bin files on your SD card. Import to Dolphin: wii nand download dolphin