Ignore those. If you get this far it likely works. I've not tried this particular extension but I think it uses the same interaction as envelope. When it is called it requires a 4 point path and an arbitrary path in the selection. It deforms the arbitrary path to fit inside the 4 point path. You'll have to play with selection order to decide which comes first.
Yeah - I am following Tav's short tut in his manual, using a star and a four-point rectangle with it's nodes moved a little. I have tried all kinds of combinations of selection and converting to paths, but so far there is no perspective/envelope effect to be seen. At most the star distorts and becomes massive and in no way resembles a star or what it should look like (mapped to the rectangle).
I guess it's broken for now.
/d