Hi,
You need only reference to
System in your project.
Then in using clause add
System.IO.Ports.
Class name is SerialPort and you don't have to put it on your form. You can instantiate it from your code:
var sp = new SerialPort();
sp.BaudRate = 9600;
sp.PortName = "COM1";
..
[Update]
I just arrived home from work and run Visual Stusio 2013 Express. There is a tab 'Components' visible by default and there is SerialPort item on it.
If you don't have this item simply just click Right Mouse Button on that tab and select option Choose Items. Then go to the .NET Framework Coponents tab and start typing Serial Port on Filter textbox. Then just click on item SerialPort on the list above to highlight that item and then Click 'OK' button.
Another option is to select Reset toolbox option to get back to defaults.
Cheers!