EagleRock has produced a six part video tutorial series that will take you from zero knowledge of CAD software, such as DraftSight, to the proficiency level required to draft complex countertops.
Be sure to watch the videos in full screen and in high definition, to be able to see all of the detail of the screen. For full screen, click the brackets on the right first, and after select 720 from the gear button: 
We suggest that you grab a copy of our written documentation and have DraftSight open as you watch these our tutorials. If you are unable to watch these videos near your CNC machine, you can download DraftSight for free and install it on another computer. Just go to DraftSight's download page: http://www.3ds.com/products-services/draftsight-cad-software/free-download/. You may notice some slight differences if your downloaded version differs from the version on the CNC machines, however, you should still be able to follow along with the tutorials.
Tutorial 1 - Introduction to DraftSight
Tutorial 2 - Coordinate Systems and the Draw Toolbar
Tutorial 3 - The Modify Toolbar
Tutorial 4 - The Modify Toolbar
Tutorial 5 - Importing Sink Cutouts
Tutorial 6 - Example Drawings