...
// define how many fields we want to store (default def is 10)
#define CONFIG_FUNCTIONS_MAX_LENGTH 8
#include <ConfigCommander.h>

// define a constant for each field slot (optional to improve the code readability)
#define CONFIG_NAME 0 
#define CONFIG_IP 1
#define CONFIG_GATEWAY 2
#define CONFIG_MASK 3
#define CONFIG_DNS 4
#define CONFIG_SERVER 5
#define CONFIG_SERVER_PORT 6
#define CONFIG_MAC 7

ConfigCommander MyConfigCommander;
...
void setup() {

...

// define config fields size
MyConfigCommander.setSize(CONFIG_NAME, 20);     // device name: 20 char
MyConfigCommander.setSize(CONFIG_IP, 15);       // ip: 15 bytes
MyConfigCommander.setSize(CONFIG_GATEWAY, 15);  // gateway: 15 bytes
MyConfigCommander.setSize(CONFIG_MASK, 15);     // mask: 15 bytes
MyConfigCommander.setSize(CONFIG_DNS, 15);      // dns: 15 bytes
MyConfigCommander.setSize(CONFIG_MAC, 17);      // mac: 17 bytes
MyConfigCommander.setSize(CONFIG_SERVER, 30);   // server domain: 30 char
MyConfigCommander.setSize(CONFIG_SERVER_PORT, 4);   // server port: 4 char

MyConfigCommander.initialize();                 // clean memory on new boards

...

// print current board name
char boardName[21]; // field size plus terminator
MyConfigCommander.readConfig(CONFIG_NAME, boardName);
Serial.print(F("Board: "));
Serial.println(boardName);

...

// store a new board name
char newBoardName[21] = "My Device"; // field size plus terminator
if (MyConfigCommander.saveConfig(CONFIG_NAME, newBoardName)) {
	Serial.println(F("Saved"));
} else {
	Serial.println(F("Fail"));
}

...

// read ethernet settings
byte mac[6];
byte ip[4];
byte gateway[4];
byte dnsServer[4];
byte subnet[4];

MyConfigCommander.readIP(CONFIG_IP, ip);
MyConfigCommander.readIP(CONFIG_GATEWAY, gateway);
MyConfigCommander.readIP(CONFIG_DNS, dnsServer);
MyConfigCommander.readIP(CONFIG_MASK, subnet);
MyConfigCommander.readMAC(CONFIG_MAC, mac);

Ethernet.begin(mac, ip, dnsServer, gateway, subnet);

}