Flow Action Components -
Enabling your org for local Flow Actions
In the Spring '18 release, you can request that your org be enabled to use local Flow Actions, also known as Local Actions. Make this request through customer support.
Note that your org must be able to run Lightning Components. That means that it must
1) have My Domain setup, and
2) The “Enable Lightning runtime for flows” checkbox must be checked in the Process Automation Settings part of Setup.
Considerations for using local Flow Actions
We recommend that you not use html markup in the Lightning Components that you use with local Flow Actions. In this respect, local Flow Actions are different from their cousins, the Flow Screen Components, The reason for this is that local Flow Actions tend to execute very quickly, and any markup you add to them will likely flash on the screen and disappear before the user can make sense of it. Local Flow Actions are best used for work that takes place in the background. If you want to take advantage of Lightning Component markup and display UI to users, you should use Lightning Components as Flow Screen Fields.
Which Method of Integrating Lightning Components into Flow Should You Use?