Enlighten reflections are applied using UE4 reflection environment rendering in the same way as UE4 static reflections. The key difference is that Enlighten reflections are updated in real time to match the rest of the lighting.

Enable Enlighten reflections

Add a Box Reflection Capture or Sphere Reflection Capture to the level.
Configure the position and influence volume of the actor as described in the UE4 documentation.
With the actor selected, in the Details window, enable Enlighten > Use Enlighten.
Run the Enlighten precompute to generate Enlighten data for the reflections.

Change the reflection resolution

Enlighten reflections are rendered using a cubemap for each Reflection Capture actor.

To set the resolution of the cubemaps in your project, in Project Settings > Plugins > Enlighten, use the Cubemap Resolution property.

This applies to all reflection capture actors which have Use Enlighten enabled.

When you increase the cubemap resolution, the latency of Enlighten updates may increase significantly in a level containing many Reflection Capture actors.

To see the effect of changes to this property, restart the editor and rerun the precompute for all levels.