Hmm. I remember I had difficulty placing objects initially, but it was because I was attempting to place items from the left pane in the Root Template rather than the right one.
In regard to the terrain, why do you have so many terrain layers?
The reason your paint is jagged has to do with the interaction between the base layer texture and the added layer. When you paint a texture onto the base layer, this jagged effect will happen wherever the boundaries are. I've found that it's a good practice to paint the entire base layer with one texture before putting other ones on.
For you, this would mean that you paint the entire map with whatever texture you used for your base layer. It'll look like nothing's happening, but when you paint the sand on top, it'll be a much more smooth transition.
