how do I create an nndoc group to archive messages into?

[Frank Fredstone]

If I add an nndoc group using gnus-group-make-doc-group and create the
file that it points to using touch, I can't enter the group, it says
the group contains no articles. If I try to move an article into it,
it says the group doesn't exist and asks if I want to create it. If I
say yes, it says no such function nndoc-request-create-group.