Floors are terrain, any floor texture can be used by any of the terrain tools, similarly objects for object tools and walls for wall tools. In this folder you want to have three more folders, floors, objects, and walls. I don't know if it's still an issue, but it use to be. Now you can create a folder, name it whatever you want, but avoid special characters. Which, I now realize you refer to in the title, so you've probably made it this far. In that directory you will find a data folder, and in that a collections folder.
Too start, you need to navigate to your steam directory, and find Dungeon Painter Studio. I can't dig up the little infographic that Pyro has posted before, but it's not too complicated.
