To do Add Mechanism you must select a Plane.  

When you do Add Mechanism, we add for you a:

•Mechanism element to the Assembly-Tree as a child to the Plane you select,

and a

•Mechanism-Editor workspace with its name-tab, graphics-area, XY-axes, and a Base-Part.

You build you model in the Mechanism-Editor workspace with kinematic elements, Solid elements, Function-Blocks, ... .

You must add a minimum of one Mechanism-Editor.

The Mechanism-Editor workspace:

Graphics-area : to which you add Kinematic and Machine elements, Kinematic and Modeling Function-Blocks, Solid elements, Force elements, and other elements.

Name-tabs : each Mechanism-Editor has a name tab.

The Base-Part (not shown in the image above) is a child to the Mechanism-Editor. It represents the frame, or the stationary part, of the Mechanism workspace. The XYZ-axes of the Base-Part are coincident with the XYZ-axes of the Plane you select when you add the Mechanism-Editor.

Mechanism menu

Model elements toolbar - left of the graphics-area - add Planes and add Mechanism-Editors to Planes

Kinematic elements toolbar - left of the graphics-area - add the basic kinematic elements to build kinematic-chains

Machine elements toolbar - left of the graphics-area - add more complex elements

Function-Blocks menu :

Kinematic Function-Blocks toolbar - right of the graphics-area - plan and measure the motion of each kinematic-chain, analyze and calculate cam-coordinates

Modeling Function-Blocks toolbar - above the graphics-area - tools to help you do more complex modeling

Forces menu

Force elements toolbar - right of the graphics-area - measure force, torque, and power that is required to drive each kinematic-chain

MD-Solids menu

MD-Solids toolbar - above the graphics-area - extrude Solids from sketch-loops, add Holes, add extrusions to all or one Part