Lesson 1: the background (bg) consists of 4 layers (0,1,2,3). You can stack bg tiles by placing tiles on different layers. Example, layer 0 can be then ground. Select 0 at the bottom and place grass tiles in an area. layer 1 can be trees, so select 1 and place trees.
You can toggle which layers you see in the editor with the "0 1 2 3" on the top screen.
Lesson 2: placing bg tiles is as simple as selecting the tile you want and placing it on the map editor. You can rotate or flip tile to get them in the position you want using the button options below the tile selector area on the right. (H)=horizontal flip, (V)=vertical flip.
The frown face is the undo button (careful, you only get one), and the 0 to the right is degree of rotation. On the far left are the tile placement options ie. single tile, fill area, etc.
Lesson 3: when your map is good to go, select save at the bottom. This save option will allow you to open the map back in the editor to continue to work on it. SC save will save each individual layer of the map if you want to use it in your program.
That pretty much sums it up. Note that some people have created more user-friendly map editors but I can't think of any keys at the moment. Hope this helps
