Now I will assume that you have completed part 1 and that you have a space ready in your Editor.
1. Simply right click "Cube" or any other brushes that you wish for from the side bar.
2. Fill in the required information for the brush.(Just experiment with different values)
3. Left click "Build" and your red wire frame brush should instantly change its looks to your wanted brush.
4. Now you probably would love to move this brush into your special spot in the room. =DLeft click on the wire frame model, so that it will be bright red. Hold down "Ctrl" while you press and hold Left mouse button, Right mouse button or Both mouse buttons.
Now try to move your mouse and see how this wire frame model is moving around. Try to see if you can move your brush to your heavily desired place.
5. Press "Add" if you want the space inside your brush to be filled.
"or" Press "Subtract" if you want the space inside your brush to be removed.
Congratulations, if you did this correctly, you now have added a brick or some other brush of your choice into the map.