https://youtu.be/QWvPXeShczk?si=3MjKQO-OUTWwNihx
The project comes as a complete project but can be migrated or copied to your own project with some consideration For the assets and the level to work correctly you are required to enable certain engine features and plugins.
If the main level doesn't appear it might be that you haven't enabled some of these settings and plugins
It is not recommended to have nanite enabled on the foliage assets as it will slow down the performance by a lot.
By default the project is configured to be running in dx11 mode to maximize performance if you wish to enable dx12 to have access to nanite and raytracing you’ll need to switch to dx12 rhi as well as check the sm6 check box in the project settings