Step 1: Editing and Placing the Components
Now place the components on the Arduino shield (inside the purple rectangle). I resized the shield by dragging the purple outline so I could place all the LEDs in a row.
Step 2: Routing the PCB
The green lines, called "airwires", denote the electrical connections that you need to route as copper traces. These come from the breadboard design you made earlier. This process of is called "layout".
Switch to the routing tool and click a pad to get started. Route the trace by moving your mouse and clicking at intermediate points until you reach the other side of the airwire. Make sure not to cross or come too close to other lines. The tool will show a warning when you make a mistake.
Repeat this process until all green airwires have been routed. You can also draw connections on the other side of the PCB if this make routing easier. You can switch and route traces on the other side of the printed circuit board by selecting the correct layer in the selector. It is even possible to switch layers while in the middle of routing a trace. In doing so a small hole called a "via" gets added to the trace, this hole will be plated with copper and conduct electricity to the other side of the board. If your board has 4 or 6 layers instead of 2 layers the drill holes for the vias will go all the way through the board but only electrically connect the two layers associated with that part of the trace.