You are going to have to make a terrain mask! I'll explain how to do it with Gimp

. Open your height map (if you made one), and copy the image. You will then copy that image on to a blank pallet (make sure you select the rbg colors instead of grayscale when opening!), and open your layers box. Anchor the layer, and make a new transparent layer. This will be where your different terrains will be made. Open your color box, and make pure green, pure blue, and pure red (meaning that the red knob will be 255 and the other color knobs will be 0). Fill the empty layer with the blue, and then make that layer transparent so you are able to trace over your height map, for better accuracy. The transparency of that layer should be about 60% to properly trace. You will then need to take your green and red, and trace over other areas that you want as different terrains. When you are satisfied with your terrain mask, delete the height mask and make the transparency 100% again (it should look like a huge blue, red, and green mess XD). Save your image file as a jpg file and a png file in your feralheart terrains folder, and then go into the map maker. Type in your file name in the terrain mask box, and use the knobs to select your terrains! Woo a lot of typing; I hope this helped you dear XD