You can select a layer from your composition to be used as texture map in Element. Select the layer you would like to use, in the Custom Layer Custom Texture Maps parameter. In the scene interface click on the desired texture slot, and click the wing next to where it says load texture. Then select the Custom Layer that you loaded your layer into. One useful way of using this is adding video to objects that would have screens (cell phones, tvs, ect). You may need to pre-compose the layer you want to use as the texture, if it has additional effects or is multiple layers.
Screen Animations Tutorial
Animate the iPhone 5 screen
Prepare the model for Element 3D
Work with multi-object materials