How do i create Material IDs/Elements in Blender? (to have differen t Meterials on one Object etc...)

Hello there,
my problem is the following:
I read here A new, community-hosted Unreal Engine Wiki - Announcements - Epic Developer Community Forums under the topic “materials”, that i have to apply placeholder-materials in blender to the mesh, to have this different material-elements in UnrealEngine 4 on my static mesh, but I cant figure out, in which way i have to apply the material in Blender, to work with UE4. Every option i choosed so far went wrong(marking the faces → then assigning to the material) and simply didnt work with UE4. Is there a special clue to solve this?
What do I have to do exactly?

it would be so great, if someone coud help me.