There tutorial series will go over the processes of creating a procedural environment.
All video here: https://www.sidefx.com/tutorials/post-apocalyptic-ruins-for-ue4/

The tool will convert a blockout into a more final version of the terrain. You can quickly make levels and tweak levels made with the tool since it is a procedural setup.

Using procedural techniques in Houdini, you can learn how to put your whole level design logic into a single digital asset for use in UE4. Using geometry for blocking out the level, you will build an asset that creates the terrain then adds details with a series of nested assets that define the different parts of the level. Controls will be available in UE4 to tweak the results. When you are finished, you will have a high level tool that can be used in UE4 to create many level variations. You can also scale up to create even bigger levels.

Quixel assets are used in the project.