Hi,
You can simply and cheaply connect a pic to the usb port of a pc with one of these far east boards and matching usb dongle, under GB£10 for the pair, much cheaper than Dwengos price for what seems to be the same thing.
I got one the other week, worked first time.
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You just use the direct Usart serial port pins of the pic.
( that is the not the same as the RS232 serial port connector which is high voltage )
Have you got a Dwengo starter board ?
What Complier are you going to use ? plenty of program code examples and tutorials for serial communications in this forum.