Assign textures to Blender Suicidator city mesh

I've generated a Blender Suicidator fbx file of a basic city. However, the city model is without textures. I have found the textures, but the city model mesh is in one piece, ie, it is a single mesh so I cannot assign the different textures to the different buildings and parts of buildings.

How do I make the city with the buildings and parts as separate meshes so I can assign the appropriate textures to them?

Many thanks in advance.