I need the correct terminology to search for answers

Projects General Guidance
2

One way to do it, assuming 'frequency' is three bytes:

byte message[] = 
{
  0xFF, 0x4C, 0xCF, 0x52, 0xA1, 0x57, 0xF1, 
  0, 0, 0,  // 3 bytes of frequency
  0x00, 0x05, 0x07, 0x05, 0x00, 0x05
};

unsigned long frequency = 903300ul;

void send()
{
    message[7] = frequency >> 24;
    message[8] = frequency >> 16;
    message[9] = frequency;

   device.write(message, 16);
}