Import Nanite mesh:
In Quixel Bridge, Download, if the mesh can be used by nanite, it has the download option:
To check if the mesh are nanitable:
In UE, Lit → Nanite Visualization → Triangles (Those in black shape, not in triangle forms, are not nantiable)
To make the mesh become nanite:
double click on the mesh → Details → build nanite
Or during import if it’s fbx. enable nanite option
R click on the mesh, choose Nanite, enable