If this is the first time you're programming a Circuit Playground board, you'll need to set up the Arduino IDE with support for it. Follow the instructions found here, and come back once you have everything working.
The code we'll be using is based on the example sketch written for the Pulse Sensor Amped. Code has been added to control the Circuit Playground's built-in Neopixel LEDs and record changes in interbeat interval values (IBI), and calculate a relaxation rating based on how often the IBI plots change direction.
Download the code from the project's GitHib repository here:
Unzip the downloaded archive and rename the folder named "Meditation_Trainer-master" to "Meditation_Trainer".
Inside that folder, you'll find a file named "Meditation_Trainer.ino" - open it in the Arduino IDE and upload it to your Circuit Playground board.