Hi Rusbaron,
Are you looking for something that will procedurally create a level for you in Unreal Engine 4? If so, that functionality is not built into the Editor. However, there are some third-party options that may be helpful in that regard. World Machine is a popular tool for creating terrain. You can use it to create pretty much any terrain you want, then use the heightmap that it gives you to create that terrain in the Editor. There is a tutorial on our Wiki explaining how to use World Machine with the Editor, and that should get you started.
Once you have the terrain you want, you will still need to fill in all the details of your level such as foliage, buildings, etc. Foliage can be done using the Foliage Mode in the Editor, but you will need to have meshes to use for it. You can use some of the meshes in the included starter content, but if you want anything more than that you will need to import the meshes into the Editor.
For buildings and other details of your level, you will need to set all of that up yourself.