1. Download and install the Teensy loader application. https://www.pjrc.com/teensy/loader.html
2. Download the chordstrum-t32.hex (Teensy 3.2) or chordstrum-tlc.hex (Teensy LC) file.
3. Run the Teensy loader application. Click the “Open HEX File” toolbar button. Navigate to the downloaded chordstrum hex file and click “Open”. (If there is a message saying file is to o big, just ignore it.)
4. Connect your Teensy to the computer using a micro USB cable.
5. Press the button on the Teensy. The Teensy picture in the app should go from dim to bright.
6. Click the “Auto” toolbar button if automatic mode is not already selected. The auto button should be bright green, and the hex file should start uploading.
7. When upload is complete, you may disconnect the USB cable.

For a more elaborate description on how to use the Teensy loader, there are platform specific guides on the PJRC website.