To align shapes, you need to have more than one shape in the workplane.
Select another shape(cylinder) from the right-hand side of window and place it anywhere in the workplane.
Select the shapes by making a box around both shapes. Click on Align or press L, this will show the alignment arrangement as shown above.
The black circles mark the corners and the centre of each axis. These are the anchor points for aligning the selected shapes. For example, let’s take the centre one, which will align the shapes in the centre of the axis. The orange outlines show where your shapes will be positioned after aligning them. Click the circle and your shapes will be repositioned. When you are done, click anywhere outside of the selected shapes to close the tool.