Arduino 1 - adc for acquire signal

Hi everyone.
I have to monitor an analog signal using arduino Galileo, but i'm still waiting for it to be delivered, so I tried to use arduino 1 to acquire the signal, using the analog digital converter (adc).
The sketch i wrote is the following:

#define N 400
int a[N];
int tempo[N];
int val = 0;
int i = 0;
int j = 0;
int counter = 0;
int button = 7;
int start = 0;

void setup()
{
  pinMode(button, INPUT);
  for (i= 0; i<N; i++)
  {a[i] = 0;
   tempo[i] = 0;
  }
  Serial.begin(9600);
}

void loop()
{
  start = digitalRead(button);
  delay(1000);
  if (start == HIGH)
  {
    for(i=0; i<N; i++)
    {a[i] = analogRead(A0);
     tempo[i] = millis();
    }

    for(j=0; j<N; j++)
    {
    Serial.print(tempo[j]);
    Serial.print(' ');
    Serial.println(a[j]);
  }
    
    delay(5000);
  }
  else
  {delay(2000);}

}

I found that arduino 1 acquire with this script at a frequency of 9,1kHz (Which is great to me!).
The number of sample N is limited by the SRAM of the Arduino, so if i use the millis function to monitor the time, the maximum number of sample that i can acquire is about 425.
However i found in the help that there is the possibility to write data (or informations) in the EEPROM memory. I know that if i have to write and to store data there the sampling frequency will decrease, but i would like to try... Maybe it will be accettable to me!
I read that i have to use the PROGMEM command, but it was really hard to me to understand how does it work.
So the question is the following:
how can I write an array (or more) on the EEPROM memory?

Thank you very much.

Moderator edit:
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tags added.

how can I write an array (or more) on the EEPROM memory?

If you have installed the IDE you can check the EEPROM examples from the EEPROM lib.

read that i have to use the PROGMEM command, but it was really hard to me to understand how does it work

For your application, it doesn't work.

Thanks for answering...
Why doesn't it work?

Because without rewriting the bootloader, you can't write to PROGMEM from a running program