Unfortunately its not possible to add xmls and vox files to sandbox maps or campaign yet. it should be possible in the future though, its up to the devs to add that functionality.
Its for version 0.5.0.
You just unzip it and place it inside documents->teardown->mods
(Everyone will eventually have to switch to 0.5.0) 🙂
Hope you figure it out!
Both versions are in the new file, that is why it is twice as big. You are right though, it is a bit confusing. I should have deleted the old version. Done that now.