To initiate the OAuth authorization flow, use your application's client_id and redirect your user to Get Authorization Code endpoint. Once the Calendly user grants access, their browser is redirected to your application's specified redirect_uri and the Authorization Code is passed inside the code query parameter.
To retrieve the access token, make a POST request to Get Access Token endpoint. Use it to access Calendly resources on behalf of an authenticated user.
Note:
Access tokens expire after 2 hours.
Use a refresh token to get a new access token.
Refresh tokens don't expire until they are used.
To test the access token, make a call to the Get current user endpoint.