Before we continue with applying materials to our brush faces we will "fix" our subtractive level according to article How To Fix Subtractive Level. You can do it or you can skip it - it's completely up to you. It affects mostly the build times.
Unlike in previous Unreal Engine versions you can't apply textures to brush faces - you always have to apply material to the face. We'll cover Generic browser basics and we'll use only stock materials available with default UT3 installation. Although textures can't be used directly anymore, the process of applying materials is traditionally called "texturing".