Overriding an action with a Lightning component closely parallels overriding an action with a
Visualforce page. Choose a Lightning component instead of a Visualforce page in the Override
Properties for an action.
However, there are important differences from Visualforce in how you create Lightning components that can be used as action overrides, and significant differences in how Salesforce uses them. You’ll want to read the details thoroughly before you get started, and test carefully in your sandbox or Developer Edition org before deploying to production.