Alright, there are a few ways that I can get audio into Layers. How I choose to accomplish this depends on my end goal.
My first inclination is to create a new, empty Layer. To do that I can either click the + button in the Sourcepane divider or go to Edit > New Layer. Pressing ⇧⌘N at the same time will also do the same thing.
I now need to get an Asset into a Layer. Drag the Asset on top of the Layer name in the Layers List to add the asset.
The other option, which is a bit less manual, is to simply drag the assets into the Layers List which will create new, individual Layers containing the assets that I've dragged.
So, I've added all of my assets to Layers. Now I need to get them laid out on the timeline since each Layer starts at the beginning of the project, which obviously isn't right. I could adjust and move them manually, but I'm sure there is a quicker way.
In the Actions List there is an Action called Arrange. This Action will arrange the Layers in the order they are in the Layers List and apply spacing based on my Layer Defaults in Preferences > Project.
Later on, I might decide that I don't like the current order of my Layers. To re-arrange my Layers, I can just drag and drop them in the preferred order in the Layers List and run the Arrange Action again – the waveform view will be updated after doing this. If I'm not happy with the spacing, I can manually edit the spacing values in the Layer popovers and run the Arrange action once more.