Should be straight forward - but you need to start from the publishing window (click the "publish" cloud at the main screen).
In that window, you'll find a tab for "Publishing games" ("Legge ut partier").
On that tab, you'll find a button: "create/update pgn files". These files are intended as a starting point for entering moves and thus automatically create onlilne viewable games. But, the files should be exactly what you and Livechess want: PGN headers only.
You should also be able to get PGN files back from livechess with the moves included. Please keep me posted if there is any room for improvement in the livechess integration - I don't use it too often myself.