AREAL3D materials can only be assigned to faces (and connected surfaces).
You can assign a material in many ways :
Toolbar
Pick the material from a toolbar and paint it on the surface (face by face or with the mass brush)
Picker
Pick the material from a face (within AREAL3D Paint Tool) and paint it on the surface
Material palette
You can insert a material palette anywhere in the 3d-space and then pick materials from it (>> context)
Selection
Select faces and click on the material in the toolbar ! (Here, once after sketchup was loaded, you have to once select the SELECTOR to activate this function).
Selector - Context menue
In teh context of the SELECTOR you will find many useful tools like auto-material, random groups of materials etc.
