Reference resources:
[video]http://v.youku.com/v_show/id_XMjUzMTYyNzYzNg==.html#paction[/video]
The guy in the example uses a different program - probably some CAD software to make the house. For very basic rooms you can use the cube brush in UE4, otherwise you will need to use a real 3D modeling or CAD software.
As Fronzel mentioned, you’re probably going to want to familiarize yourself with a 3d modeling program. There are free ones out there such as Blender that are quite powerful.