Start by downloading the master translation table:

http://www.panoramafactory.com/localization_v5/pfactory_master_po.zip

Open the ZIP file and extract the translation table file:

pfactory_master.po

This is a blank translation table that contains the English strings used by The Panorama Factory (except those in wxstd.po).

Copy pfactory_master.po into the folder you created for your language and rename it to pfactory.po.  Then open and edit pfactory.po with poTree.