The level editor is built-in in the game, but you need to get a little bit dirty to use it.
You need to open file TotemTribe\data\gui\mainmenuscreen.xml and look for
This is where button that loads up editor is present, but it is commented out. You need to change the folloding things:
change that into
After you do that there should be an editor button in the game main menu. Keep in mind that we provide absolutely no support about that so use it at your own risk.
If the guide above does not make sense to you, chances are you are not technically skilled enough to use the editor, so either find someone who can help you or let it go. I will not gonna give more detailed instructions, sorry.