Once you have created your screen flow you can begin creating an "Act On It" action that will launch the flow when selected by a user.

To create a 'Screen Flow' action, follow these steps:

1. Navigate to the ‘Message Actions’ Tab (Act On It Lightning App > Application Settings > Message Actions) and click ‘New’.
2. Select the "Flow" Record Type and select 'Next'.

Configure your action button with the following details:

• Action Label: Provide a meaningful name for the action. Customize the button further by selecting an icon from the ‘Icon Selection’ section.
• API Name: Choose a unique name for the action, without spaces or special characters (except underscores). This name distinguishes between similar actions with a matching label.
• Flow Developer Name - Provide the flow's unique API name
• Flow Input Variables - Select from the list of input variables. Only select values supported by your custom flow. 
• Type - Select "Screen Flow".
• Modal Header - Custom header for your flow.
• Modal Size - The size of you screen flow. 
• Is Active: If inactive, the button will be disabled for all new and existing messages.
• Is Available: If enabled, the Message Action will be visible in the Message Type Builder.

Lastly, configure your Record Dependency settings and click "Save".

Your Message Action is now ready to be applied to any Message Type with a matching data type. Admins have control over which actions are accessible to users via their User Settings.