This exact screenshot was used as a base for those graphics mentioned above. (They are not connected to any game element so far, though. Currently they are just... there. :) )
3. Save it as "editorsetup.conf"
4. Launch the game
5. Open your levelset
6. Open Level Editor and find in elements list "User Defined elements"
7. Show it and look
You see the signs and steel walls with signs and you can use its very simply!