How do I create spheres?

Just like any other 3D body, you start with a sketch to create a sphere.  

1. Draw a vertical line, and connect the two ends with an arc to create a semicircle.
   
2. Change to 3D view. 
3. Go to Menu > Tools > Revolve and select the filling of the closed sketch.
   Optionally, select the filling first and go to More > Tools > Revolve. 
4. Select the axis of revolution. 
5. Select Done. 

To create a hollow sphere, follow these steps:

1. Draw a semicircle. 
2. Select Offset edge and select “Single” offset type. 
3. Select the semicircle’s edge and drag the edge to offset the entire sketch. 
4. Change to 3D view. 
5. Select the outer filling of the semicircle. This will become the shell. 
6. Go to Menu > Tools > Revolve. 
7. Select the axis, which the shell will revolve around. 
8. Adjust the angle of revolution to 360 degrees. 
9. Select Done.

You can watch this tutorial to see how it’s done.