We will continue to use the level that we have just created i.e. NewLevel. However, at this stage you could create a brand new level if you wanted to.
If you need a refresher on creating a new level, then click here.
From here, we can start sculpting the surface however we want it to look. We will do this directly on the surface.
To do this directly on the surface, go to the Terrain Editor, click Sculpt and activate the Raise/Lower button. If you move your cursor into the Viewport, you'll now see a green circle around it.
With the current size brush, we can be fairly precise. If you want to Raise or Lower a larger part of the terrain, you can change the value for the Outside Radius under Brush in the Terrain Editor. 5 should be a good size brush. In a level like this, a larger brush than that would probably change too much of the terrain at once.
Let's set the Height to 5. You'll see that the more quickly you drag the cursor across the surface, the less the height will increase, meaning that if you move your cursor more slowly, the terrain will increase in height more quickly.
How quickly the height increases is determined by the Hardness value. This is always a value between 0 and 1, 0 meaning it won't increase at all, and 1 meaning it will increase very quickly.
Play around with the Height and Hardness values to find a setup that works for you. Depending on the size of the level and other factors, you'll probably want to use different Hardness and Height values for different situations, so it's important that you get a good feel for how this process works.
Adjust your level until you're happy with the result.