To use the SSD1306 OLED with your Adafruit CircuitPython board you'll need to install the Adafruit CircuitPython SSD1306 module on your board.
First make sure you are running the latest version of Adafruit CircuitPython for your board.
Next you'll need to install the necessary libraries to use the hardware--carefully follow the steps to find and install these libraries from Adafruit's CircuitPython library bundle. Our CircuitPython starter guide has a great page on how to install the library bundle.
If you choose, you can manually install the libraries individually on your board:
Before continuing make sure your board's lib folder or root filesystem has the adafruit_ssd1306.mpy, adafruit_bus_device and adafruit_framebuf files and folders copied over.
Next connect to the board's serial REPL so you are at the CircuitPython >>> prompt.
You'll need to install the Adafruit_Blinka library that provides the CircuitPython support in Python. This may also require enabling I2C on your platform and verifying you are running Python 3. Since each platform is a little different, and Linux changes often, please visit the CircuitPython on Linux guide to get your computer ready!
Once that's done, from your command line run the following command:
sudo pip3 install adafruit-circuitpython-ssd1306
If your default Python is version 3 you may need to run 'pip' instead. Just make sure you aren't trying to use CircuitPython on Python 2.x, it isn't supported!