This asset pack uses NANITE and LUMEN. A RTX Graphics Card is recommended, use a RTX 2060 Super at least.
You need to enable the Procedural Foliage option in the Editor Preference to use the Procedural Generation. (Edit > Editor Preference... > General > Experimental > Foliage > Procedural Foliage)
In Unreal Engine Version 5.2 and above it uses PCG (Procedural Content Generation), make sure to enable these plugins in your project file: