The majority of Widget authoring happens within layers. Layers allow you to add new media or actions to a widget. By default, the first layer is always provided within the authoring template.
To add a layer, hover your mouse after the previous layer and a green "+" sign will appear. Click to add a new layer.
As a shortcut for creating similar layers, you can duplicate layers using the "Copy" button. A copy of the layer will be created and then you can modify as needed.
Use the up and down arrows in the upper-right of the layer to re-arrange the layers.
If you would like to permanently remove a layer from a widget, use the Delete button.