A dialog will pop up. It has two parts. On the left is a list of layers. On the right are the properties for the currently selected layer. Select the layer you want to examine or modify by clicking on it in the layers list.
Some layers are composite layers that is made up of other layers.
You can expand or contract composite layers in the layer list by double clicking on the layer name. The plus sign means that the layer is currently contracted and if you double click it will expand showing the sublayers. The sublayers are shown indented from their parent layer. The minus sign means that the composite layer is fully explanded and if you double click the composite layer will contract hiding the sublayers. After you select the layer you are interested in, it's properties will be displayed on the right hand side of the dialog box.