Sending it to the serial port is the easy bit:
SerialPort sp = new SerialPort("COM1",9600, Parity.None, 8, StopBits.One);
sp.Write(myArrayOfBytes, 0, myArrayOfBytes.Length);
Where the parameters will depend on your configuration.
The fun bit is working out what the remote equipment is going to take.
That will depend on the hardware you are expecting to talk to. Look at your hardware manual, and work out what it is expecting.