Frustum Tool

Ribbon menu Bodies tab Solids container Frustrum Tool
or
(Classic) Build Bodies/Geometry Frustrum Tool
Creates a frustum, which is a cone, the top of which has been cut off. You create a frustum by drawing its length. The Frustum tool makes the bottom radius 12.5% of the length and makes the top radius of the frustum 50% of the radius of the base radius. Before drawing, you can also specify the frustum's length and the radii of its bottom and top
Learn about Creating a Frustum.
 
For the option:
Do the following:
New Part/Add to Part/On Ground
Select either:
New Part - Creates a new part.
Add to Part - Adds the frustum to another part in your model.
On Ground - Adds the frustum to ground.
Note: Add geometry to ground if the geometry does not move or influence the simulation of your model. For example, if you are simulating a car driving around a race track, the geometry that defines the race track can be added to ground.
Length
If desired, select and enter the length for the frustum.
Bottom Radius
If desired, select and enter the bottom radius for the frustum.
Top Radius
If desired, select and enter the top radius for the frustum.
 
Note:  
Three hotpoints appear on a frustrum after you draw it. One controls the length of the frustum, one controls its top radius, and the other controls the bottom radius. For more information on modifying geometry using hotpoints, see Using Hotpoints to Graphically Modify Geometry.