How to Control a Parallax Brand Continuous Rotation Servo?

Ok so before I knew how to use an Arduino, I was teaching myself how to use C language with Parallax's Basic language.
So now that I know how to use an Arduino I would like to use Parallax's BOE-Bot Setup to make a robot that runs of an Arduino...
The problem is how to control the servos on the BOE-Bot...
In the second link, page 1, it shows a schematic with the servo connected like this:

So what I want to do is make the servo go both forward and backwards.
But the Schematic above shows a single wire to control the servo... and yes, I know the servo can go both ways.
Also in the second link, page 4, it shows how to communicate with the servo but i don't understand what it means...

Can anyone help me out?

Use the servo library.
The ex-servo should be stopped around 90 "degrees".
The ex-servo will move in opposite directions either side of the 90 "degree" point.
For finer control, use the "writeMicroseconds" method.