First of all, welcome to the forums! I hope everything so far has been good for you.
Now, to answer your questions...
An ISO (International Organization for Standardization) is an archive image file format. It is pretty much some uncompressed information that has been unified as a whole (or sometimes extracted from a cd) to be transfered to a hard drive/cd/dvd media. It is very easy to use since it is an image file containing a lot of information inside (not necessarily games, it can be programs, music, and movies). Just download it and burn it to a cd/dvd (though if it's Wii games we are talking about, make sure to brickblock it by removing the updates).
You can get some Wii ISOs by searching the net or by searching through torrent sites such as
TorrentMan.com - your ultimate source for torrents
Now, very recently there was a leaked backup loader (which made loading ISOs through HBC possible) that was made public without permission from the author, therefore I cannot point you to a direct download of it. It is a backup loader used to load ISO files through a burned dvd. I for one, have no experience with this since I recently got a modchip installed. However, there is a new open source backup loader that might be available for download and use, check it out here:
http://www.wiihacks.com/wii-hacks/56...en-source.html
As for instructions on how to use it, there are some instructions posted in the thread I pointed above.
I hope that helped answer your questions. If you're still confused, feel free to ask me anything else. Happy homebrewing!