to a usb stick (or setup an SMB share to the files)
Bannerbomb loadmii from an sd-card, select usb as source (or SMB)
remove the sd-card from wii, format and extract CB2_BB_Cios38r14_installer.zip to the sd-card, reinsert into wii.
From the loadmii screen, load usb:\boot.elf
This should start the cios installer, choose no ios reload, install