I'm also very new to this cartography thing and CC3 (only since May)...but I was in a similar situation and have spent about as much time looking for objects on Dunjinni as I have mapping (not to mention tutorials). I don't have the Tome (would like to get it), but all you have to do is download the .png to a folder (I created a "downloaded" folder in my CC3 directory - subdivided by category of object) and click on the little icon just above and to the right of the symbol viewer (just below the options button). From there you can navigate to the symbols you have saved.
Its also helpful to note that you can save the floor tiles many have posted on Dunjinni in a similar way and then use them by creating a new fill style. (Click on the FS on the top right of your screen - select the bitmap files tab - select "new" - then click "find" - locate your floor tile - then adjust the specifications for it - i.e. scaling, etc).
Hope that helps.