Salesforce admins and developers can leverage Act On It within their Lightning Flows to automatically send messages that prompt users to take action. By incoporating Act On It into your flows you immediately benefit from Act On It's advanced alerting capabilities, such as the ability to:

• Deliver push notifications via Act On It's native alerts console.
• Enable or disable additional messaging channels with a single click.
• Enable users to opt in/out and personalize delivery.
• Plug-in custom alert actions to streamline next steps.
• To track and report on message delivery and engagement. 
• Activate/Deactivate the alerts outside of flow.

To add Act On It messaging to a flow:

1. Add a new element and search for the "Publish Message" action provided by Act On It.

1. Configure the input values as follows:

• Message Type Developer Name - Required. This links the message to a predefined Message Type. The Message Type's developer name can be found here:

• Message - Optional. Override the default message from the Message Type. Useful for creating dynamic, personalized messages featuring Salesforce data.
• Recipients - Required. The target user/group IDs to receive the message. For multiple recipients, construct a comma separated list of Ids or create a list of Ids that can be passed to the Recipient List input.
• Excluded Recipients - Deprecated. We recommend using "Message Opt Outs" instead.
• Record ID - Optional. Links the message to a Salesforce record.
• Send Date/Time - Optional. Schedules the message for future delivery.
• Source - Optional. Helps track messages for reporting.

Remember to use constants for fixed values and avoid using hard coded Id references where possible. 

The Publish Message action returns output variables indicating if the message published successfully or any errors:

• isSuccess – Denotes if the action succeeded and the message is published (or scheduled for publishing).
• errorMessage – An error revealing the root cause of any failures.

By integrating Act On It messaging into flows, admins can ensure stakeholders are notified to act when needed. The action provides flexibility to deliver messages when you need, while still benefiting from centralized Message Type configuration.