Bukkit

1. Get the latest Multiverse version at http://dev.bukkit.org/server-mods/multiverse-core/

2. Set it up the usual way and make sure that you have the Nordic.jar in your plugin directory.

3. check if Nordic is loaded properly with /mv gens, Nordic should appear in the list.

4. if so, just use Multiverses create command like you used to but with the -g switch. If you would like to create the world mah_awesome_nordic_word with the seed ileikturtles you would do it like this:

/mv create mah_awesome_nordic_word normal -s ileikturtles -g Nordic

for more information on the command see the multiverse wiki: https:github.com/Multiverse/Multiverse-Core/wiki/Command-Reference#wiki-create

now you have a new world in multiverse using the nordic generator.

If you still have problems, check out the multiverse wiki page for custom wgens: https:github.com/Multiverse/Multiverse-Core/wiki/Custom-Generator-Plugins