As you know from reading the Quick Start Guide the USB port on the module acts as a power source, an interface to the IDE, and also provides serial port communications.
This allows you to use a terminal emulation application such as TeraTerm, PuTTY or CoolTerm (OS X) to communicate with the device from the USB port on your PC.
After installing the terminal emulator of your choice you will need to know which COM port it is on. In the device manager of Windows you can see this.
Next you will need to configure the emulator (PuTTY is used here). In the case above it is on COM5 so you will need to go to the Serial port settings of your Terminal Program and change it to COM5. The setting default is probably 9600-8-1-N but should be changed to 115200-8-1-N, shown below. Next go to the Session category on the left side and make sure that Serial is chosen as the connection type and then open the terminal.
When working correctly, you will see the ">" prompt and output to the terminal.
When you press the reset button on the module, you will see output to the terminal window, and some useful information depending on what you are running.
Note: Sometimes the terminal has to be reset. If you are not getting any output, close the terminal, reopen and setup serial port again.