Now that your Yún is successfully interacting with Twitter, let’s add the push button and LED. This will require two steps: first, you’ll wire the extra components to your Arduino, and second, you’ll modify your code slightly so that the Arduino knows when a new mention has come in. We'll begin with the circuit.
The push button has two wires to connect; one should go to ground, and the other should go to the pin you’re reading from (we've chosen to use pin 2). The LED also has two connections; as with the wire, one will go to ground, and the other to the pin to which you’re writing (we’re using pin 13). The short leg of the LED should connect to ground, and the longer end should connect to the digital pin, with the resistor attached to either—it does not matter which.