Update help

A friend of mine downloaded homebrew and hackmii a while back, using a youtube video as a guide. The video was about how to cheat on Call of Duty and it suggested to downgrade the wii to version 4.2. After he finished downloading and restarted the wii, the wii menu no longer popped up after the power was turned on, but a mod menu could be accessed by holding reset. After a few days, the wii menu started showing up again (I don't know how; I wasn't there at the time). He no longer wanted homebrew or hackmii due to the difficulties he had, so he formatted the wii because he couldn't figure out how to get rid of it. The wii is now at version 4.0, and most of his games will not play with that version. I have reinstalled homebrew using bannerbomb, because I assume if homebrew can downgrade a wii, it can also update. However, I don't understand how to use it very well, nor does he. If possible, could you tell me how to upgrade the wii from version 4.0 to 4.2, and link what I need to download? I've installed homebrew with bannerbomb, and that's about it.

You can update if you have a cIOS will ot be removed.