The Steam VR How-Tos contain step-by-step guides that will walk you through how to use UE4 and Steam VR together.
Beginner
The Steam VR Rift Beginner How-Tos will walk you through setting up your UE4 project to work with the Rift HMD, Touch Controllers, and the Guardian system.
Intermediate
The Steam VR Intermediate How-Tos will walk you through adjusting the color of the Chaperone System, using Touch Controllers to pick objects up, and also how to use Stereo Layers to display information to the user.