To use any of the above modules, you need to connect your Calendly account to Integromat. If you do not have a Calendly account yet, you can create one at Calendly.com.
To connect your Calendly account to Integromat, follow the general instructions for Connecting to services. When creating a connection, you will be requested to enter your API Key. A quick quide to getting an API key can be found here. Once you have copied your API key to Integromat, click on Continue and finish your scenario.