To make the grass, draw a line around the desired area for the grass then open up the Forest pack create panel and select the line and add the grass to the line. If the grass area goes over any parts where the grass isn't wanted, simply draw another line around that area. Then open up the Forest back modify panel go down to area and then add that line to the area and tick the exclude box.
The trees were assets from the forest pack which I placed down in random spots.
