You must activate the Spin with a perpendicular view from your
rotation plane.
Use the small menu on the lower left of your 3D Viewport to control
the segmentation and angle for the Spin.
Control the direction of the Spin with positive or negative values for
the Angle value at the Spin options.
In Figure 4.28, you can see an example of what you can create using
the Spin.
Figure 4.28 - Rounded shape from the Spin
To use the Spin, you have to go into Edit Mode and select your model's
parts to replicate with the Spin. For instance, we can select the face
from a shape like the one shown in Figure 4.29.