Community owners can obtain an API key via Settings → API. Whenever calling an endpoint, just pass the base64-encoded API token in the header like this: “Authorization: Token [base_64_api_token_goes_here]”.
For example, to get a list of all the communities someone owns:
curl -d "" -X GET [<https://app.circle.so/api/v1/>](<http://wfefewfwewef.lvh.me:5000/api/v1/get_api_key>)communities/ -H "Authorization: Token 3XMT8XDKxiYJWKVyaUmN7db8"