I think you need to understand the node editor a bit better. This is where you plug and unplug nodes, to create a work chain that ends in your planet node. Generally you start with your landscaping displacements, into a compute terrain node (which generates mapping cordinates and geometry normals (slope)), then you tend to use surface layers to apply texture, before plugging into the planet.
You can access available nodes by right clicking in the node editor window, and going through the drop downs. This is how most work is done in TG. I rarely use the left pannel of the program, except to leave up my render settings dialogue.