First, the addon has nothing to do with sculptries, If you export your mesh to sculptries and export it back to blender you should rescale it back to were it was.
Second, You need to copy the folder “io_unreal_engine_fbx” which contains 2 files “init.py” “and export_unreal_engine.py” to your blenderFolder/2.73/scripts/addons
then start blender and go to “User Preferences” click on “Add-ons” tab and from the left menu click on “Import-Export” then in the right side of the window you should see “Import-Export UnrealEngine4 FBX”
just tick the box next to it to enable the addon.
Hope that helps.