Go to Settings > Integrations and Keys, click New key, and search for CircleCI. Click Continue, specify a key name and click Save.
In the Integrations list, where your key is now included, click Authenticate.
Provide your CircleCI API token.
Useful link:
Now that you've configured your integration, add one or more of the integration's actions to an automation, test the automation, and then add the automation to an incident type.