For the material take a look here:
.unrealengine.com/latest/INT/Engine/Rendering/Materials/HowTo/Transparency/index.html
But I still find reflections an translucent materials buggy. There is also an option to magnify the reflection effect, but it does not work on translucent materials.
Also you need to add a reflection capture and don’t forget to build your level (lighting)
Look here: