Getting an invalid import file extension

[Royas]

I'm trying to import the "We Be Goblins" package from the Realm Works free content page, but every time I attempt to do so, I get an error message "does not have a valid Realm Works export file extension" and I can't go any further. I tried to see if Realm Works needed updated, but it seems to be current. The file is titled "WeBeGoblins.1.0c.rwsecure" and I have made no changes to the naming format. What do I need to do to import this into a realm? Thanks in advance.