First make a Cubemap, theres a free tool from AMD here.
You will also need 6 images for the cube faces rotated like so:
The AMD tool ModifiedCubeMapGen.exe pictured below will allow you to export a .dds file that can be dragged into Unreal.
In the unreal level grab the Skylight and set it to use Sourcetype / SLS Specified Cubemap drag your cubemap into the slot
if you want reflections below the horizon then unset Lower Hemisphere is Solid Color
Now make a shiny chrome material something like this and apply it to reflective stuff in the level it will show up the cubemap.
I just have a super simple spot pattern as my cubemap, I get this: you would be able to get fancier results with more photographic images so thats up to you to google