How to Upload a Sketch to an Arduino
The content of circuits and Arduino sketches can vary greatly. Before you get started, there is one simple process for uploading a sketch to an Arduino board that you can refer back to.
Follow these steps to upload your sketch:
Connect your Arduino using the USB cable.
The square end of the USB cable connects to your Arduino and the flat end connects to a USB port on your computer.
Choose Tools→Board→Arduino Uno to find your board in the Arduino menu.
You can also find all boards through this menu, such as the Arduino MEGA 2560 and Arduino Leonardo.
Choose the correct serial port for your board.
You find a list of all the available serial ports by choosing Tools→Serial Port→ comX or /dev/tty.usbmodemXXXXX. X marks a sequentially or randomly assigned number. In Windows, if you have just connected your Arduino, the COM port will normally be the highest number, such as com 3 or com 15.
Many devices can be listed on the COM port list, and if you plug in multiple Arduinos, each one will be assigned a new number. On Mac OS X, the /dev/tty.usbmodem number will be randomly assigned and can vary in length, such as /dev/tty.usbmodem1421 or /dev/tty.usbmodem262471. Unless you have another Arduino connected, it should be the only one visible.
Click the Upload button.
This is the button that points to the right in the Arduino environment. You can also use the keyboard shortcut Ctrl+U for Windows or Cmd+U for Mac OS X.
Now that you know how to upload a sketch, you should be suitably hungry for some more Arduino sketches.