Need to open viewer on FG monster

Been trying to understand how to open up the viewer and load up the
Korvaak Scion enemy, but all i see are the non FG enemies on the viewer.
I also tried using the manager to extract the gdx2 files but that didn’t work
and i got some error telling me some extractor program had failed.

Is there any “for dummies” how to successfully open up the FG enemies in the viewer ?.