To assign an object or a collection of objects to a layer simply select it (or them) and choose the desired layer e.g. Audio Circuit Paths, from the dropdown box on the left of the Position toolbar. This is normally found just above the Library List.
Tip: do not change the layers of symbols. Instead only select the cable/dogleg objects that you want to move to the new layer.
Once you have selected a layer, all new objects that you create will be placed on that layer, until you select a different layer. So in normal use it is good practice to select the layer you want, then draw all the connections for that layer.
Regarding the difference between the Dogleg tool and the Cable tool, the Dogleg is for simple connections and the Cable is for more complex connections. Click and drag to create a Dogleg - it always has 3 segments (2 horizontal and 1 vertical). For connections with more segments always use the Cable tool. Click once to start drawing the Cable, click once to set each corner or 'vertex' and doubleclick to finish.
I hope this is helpful.
Kind regards,
Rob Robinson
Stardraw.com