To install an add-on, simply run the krang_addon_installer on the
add-on package. For example, if you installed Krang into
/usr/local/krang and you want to install Turbo-1.000.tar.gz:
/usr/local/krang/bin/krang_addon_installer Turbo-1.000.tar.gz
Another way to install an addon is to use the --WithAddon option
for krang_install when you're installing Krang:
bin/krang_install --WithAddon Turbo-1.000.tar.gz ...
For more information about add-ons see Building a Krang Add-On.