Need help reinstalling homebrew channel on 4.2

You will have to find a hack for 4.2.

4.2 patched the exploits that worked on 4.1 and below.

IF you installed bootmii before upgrading you may be able to do a restore and get your Wii back to a pre 4.2 status.

That is all I can tell you.

I can better explain it sortof.
Use this: http://hackmii.com/2009/09/indiana-pwns/
Read it understand it.
http://hackmii.com/2009/10/hbc-freeze-fix/
Put this aswell.
It will also reinstall bootmii.
If you could install bootmii before hand you still have a bugged boot1 they wouldnt dare to fix that.
however your have a upgraded boot2v4.