Download the bannerbomb v2 and unzip the file to your SD-Card (make sure to remove ANY OTHER Wii data from the private directory otherwise it will NOT work!)
Download the HackMii Installer and put the boot.dol in the root of the SD-Card
Start the Wii, remove any disc
select the SD-Channel (bottom left)
insert the prepared SD-Card and wait for the Start boot.dol?-prompt (if it freezes, hold Power-button to reboot the Wii then try again)
select Yes
follow the instructions (you most probably want to install all 3 options – try to install BootMii as boot2, if it doesn’t work, install as IOS)