In addition to the Arduino IDE software itself (if not already installed), three downloads are required:
First, retrieve the thermal printer Arduino library the Arduino library manager.
Open up the Arduino library manager:
Search for the Adafruit Thermal Printer library and install it
Second, download Cryptosuite, another Arduino library. When extracted, rename this folder to Sha and confirm the files sha1.cpp and sha1.h are inside this.
Finally, download the Adafruit "Tweet Receipt" code from its own repository, extract the archive and then rename the uncompressed folder to Gutenbird. Confirm that this folder contains the file Gutenbird.ino. This code is reliant on Arduino 1.0 features and will not work with Arduino 0023 or earlier.
Place the Thermal and Sha folders inside your Arduino libraries folder. You may need to create this folder if it does not yet exist. In Windows, this would be (home folder)\My Documents\Arduino\Libraries. For Mac, (home)/Documents/Arduino/Libraries. And for Linux, (home)/sketchbook/libraries. We also have a great tutorial on Arduino library installation at:
Place the Gutenbird folder inside your Arduino sketch folder (one level above the libraries folder).
After installing the libraries and sketch, restart the Arduino IDE. You should now be able to access the Twitter sketch by navigating through the menus: File→Sketchbook→Gutenbird