Measuring calmness using Muse

Hi everyone!
I’m developing a meditative experience and want to use Muse data to measure the calmness of the user.
I know you can use Muse Direct to stream the EEG data, but I am unsure as to how I can measure the calmness of the user through the data or processing the data correctly. I want to get similar data that you see when using the Muse app.

If you guys can point to resources or studies that can help me do this, that would be great.
Thank you!