Using the VR editor
Unreal Engine comes equipped with a very capable virtual reality editor that allows you to build your scenes entirely from within the virtual environment. Nearly any editor operation you might need to perform can be done without leaving VR.
It may be tempting, though, to look at the VR Mode editor as a gimmick when you first encounter it. After all, what's wrong with the existing editor? Nothing, but here's the thing: virtual reality isn't a flat screen. Depth exists. Sightlines are different. Colors render differently. Developing for virtual reality by using a flat screen adds a layer of abstraction to your design process. You'll understand more and get better results by working directly in your target medium when you can.
In practice, you're likely to find both editing modes useful. Just as it's difficult to see what a scene is really going to look like in VR from the flat-screen editor view, it's difficult to achieve precision in placing objects in VR Mode. You'll discover...