To push Alerts into 411 (from another alert system), you'll need to configure a "Push" Search. Once you've saved the new Search, you should be provided with a push url.
This is the endpoint you'll have to push Alerts to. You'll also need your API key, which you can grab via your user page.
With these two pieces of information, you're ready to start shipping alerts into 411. The /api/alert/push endpoint accepts a JSON array of objects with the following fields:
alert_date: Unix timestamp indicating when the event occurred.content: The data associated with this Alert.
See the API documentation for additional details on generating API queries.
Example:
$ curl -H 'X-API-KEY: API_KEY_HERE' 'https://HOSTNAME/api/alert/push?search_id=1' -d '[{"alert_date": 1476057600, "content": {"a": "b"}}]'