The Homebrew Channel is an essential piece of homebrew that allows you to load other homebrew, when combined with Priiloader or Bootmii/Boot2, you can entirely skip loading the system menu and just load your Wii into homebrew. It is installed via the Hackmii Installer.
To install the Homebrew Channel, follow the instructions on Intro to Softmodding that are relevant to your Wii. Once done, you will be able to put homebrew applications in the /apps folder of your SD Card or USB Drive.
Controlling the Homebrew Channel
The Homebrew Channel could be controlled with the WiiMote, used like the system menu.
If you have Bootmii installed as an IOS, there is a button on the menu to launch it.
Installing themes to the Homebrew Channel
|Themes for the HBC can be found anywhere, like WiiBrew.|
If you want an alternate look to the Homebrew Channel, you can easily install themes like they are homebrew. Simply download the theme you wish to install, extract it to the /apps folder of your SD Card or USB Drive and then run it in the Homebrew Channel like it were homebrew. The theme will then be installed to the savedata of the Homebrew Channel so you can take out the SD Card or USB Drive and the theme will still be there.
To uninstall a theme, delete the savedata of the Homebrew Channel in the Wii Settings Menu.
If you wish to read more on the Homebrew Channel, please read the WiiBrew page or the (official?) page on hbc.hackmii.com