To build a world in Unreal Engine 5, I first create a new level, and then go to Window > Environment Light Mixer to add all the sky light and atmosphere into the scene.

The Directional Light is used to adjust the lighting for different times of day by changing its rotation and intensity.

To create an emissive material, I create a new material, multiply a color with a parameter, and set the parameter’s Default Value to 1.

Using FABis a great way to quickly populate a world. There are two methods to add objects to the scene: downloading and dragging them directly. Additionally, I can use Tools > Merge Actors to combine multiple objects and save the new one into a folder.
To manage the landscape, I can open Window > Layers / World Settings / World Partition > World Partition Editor / Levels for easier access to my landscape settings.

I can also create a new landscape by entering Landscape Mode and sculpting the terrain as needed.