How to write properly to STM32f411 flash using arduino - arduino

Question

I have this question because I was standing still and I don't know what to do;)
I would like to write to Flash stm32 using arduino library latitude and longitude of 3 European capitals;)
I am a layman when it comes to programming. Below is my code.
Could someone please help me how to properly write these values in flash. Then I would like to read them, but first I want to focus on writing to flash.
I use this library
https://github.com/khoih-prog/FlashStorage_STM32
#include <FlashStorage_STM32.h>
const int WRITTEN_SIGNATURE = 0xBEEFDEED;
// Create a structure that is big enough to contain a latitude
// and a longitude. The "valid" variable is set to "true" once
// the structure is filled with actual data for the first time.
typedef struct
{
int index[3];
char latitude[100];
char longitude[100];
} Capitals;
//data
int data11 = 52,211233;
int data12 = 4,532122;
int data21 = 38,024321;
int data22 = 23,443456;
int data31 = 38,024321;
int data32 = 23,443456;
void setup()
{
Serial.begin(115200);
while (!Serial);
delay(200);
Serial.print(F("\nStart StorelatitudeAndlongitude on ")); Serial.println(BOARD_NAME);
Serial.println(FLASH_STORAGE_STM32_VERSION);
Serial.print("EEPROM length: ");
Serial.println(EEPROM.length());
// Check signature at address 0
int signature;
// Create a "Capitals" variable and call it "owner"
uint16_t storedAddress = 0;
Capitals owner;
EEPROM.get(storedAddress, signature);
Serial.println("EEPROM is empty, writing WRITTEN_SIGNATURE and some example data:");
EEPROM.put(storedAddress, WRITTEN_SIGNATURE);
// ...in this case we ask for user data.
Serial.setTimeout(30000);
Serial.print("Insert your latitude : ");
String latitude = Serial.readStringUntil('\n');
Serial.println(latitude);
Serial.print("Insert your longitude : ");
String longitude = Serial.readStringUntil('\n');
Serial.println(longitude);
// Fill the "owner" structure with the data entered by the user...
latitude.toCharArray(owner.latitude, 100);
longitude.toCharArray(owner.longitude, 100);
// ...and finally save everything into emulated-EEPROM
EEPROM.put(storedAddress + sizeof(signature), owner);
// Print a confirmation of the data inserted.
Serial.print("<< Your latitude: "); Serial.print(owner.latitude);
Serial.print(". Your longitude: "); Serial.print(owner.longitude);
Serial.println(" >> have been saved. Thank you!");
}
void loop()
{
// Do nothing...
}
Thank you in advance for your help