The Shapes tool is a great way to make your designs more interesting. To access shapes, select them on the toolbar at the bottom of your editing canvas.

Once you select the shape you'd like, you are presented with more options. From here, you can adjust the color and opacity of the shape, as well as the color and opacity of the stroke/outline. You can also select the type of stroke - solid, lined, or dotted:

Once you accept, you have the entire toolbar available to you to edit the shape. In the example below, we have 3D adjusted the shape - which is a great way for more visually interesting designs.