You can find all the information you need about using the network interface here : Network interface file, pasting it unto the SD card, and resetting the card. Always make sure the polarity is correct when wiring in power inputs (coming from the Power Supply).
(There is also a DFU interface for flashing firmwares but that's mostly for developers).
The CDC (Serial) interface is the interface host programs like Pronterface use to allow you to interact with your machine.
You edit the configuration simply by editing this file in a Text Editor, saving it and resetting the board. The SD card can also be used to flash a more recent version of the firmware to your board, see where to get the binary file and how to flash it via the SD card.
It can also be used to store and play G-Code files, see Player.
Probably the machine for which Smoothie is most used, due to Smoothie's roots in the Rep Rap project, 3D printers are fairly simple to Smoothiefy.