How to display a Hypergraph? How to use?

I've got Hypergraph set up, but how do you use it to display nodes?

The only documention I was able to find was to put a tag like "[hg||600|400]" in the body.

How does that tell Hypergraph what nodes to include?

Using that tag I get an error:

General error while reading file /xxxx/modules/hypergraph/graphs/hg.php?par=2&ctl=1&src=m&dummy=.xml.
Exception : java.lang.NullPointerException
Start applet with default graph

(And then Hypergraph works, but has a bunch of long numbers.)

Obviously it just doesn't know what nodes to display - but how do I tell it what to show?