They are deliverd as wads.
Being : title.wad
Just tryed it using Twilight Hack.
1) Download
http://waninkoko.wiinewz.com/WAD-Installer_v1.zip
2) Rename wad-installer.elf to boot.elf and put on root of your SD card.
3) Put title.wad (From VC Rip) on the root of your SD card.
4) Put the SD card into your Wii (Front slot)
5) Run twilight princess, run backwards or talk to the dood.
6) It will run some lines of code, and boot up the wad installer..
6a) Press 1 & 2 until it detects your wii mote.
6b) Press A when it tells you, and wait for it to install.
The it should start installing ...
I waited 7 minutes nothing happend so
I hard resetted my Wii..
Just to note it doesn;t brick your wii.
But I wonder how long it would take ?
For info I'm using the Diddy Kong Quest vc title.wad
"put the wad installer renamed to boot.elf, but only thing i get is some code dump after it starts installing"
same here ...