Assemblies are used to define working prototypes of your product concept. You can easily add joints and forces to your SolidWorks assembly.
See Using Motion Entities for instructions on creating specific elements.
To simulate your mechanical system you create the mechanism model for the assembly.
To create a mechanism:
In the IntelliMotion Browser, indicate which components from your SolidWorks assembly participate in the motion model by using drag-and-drop.
Define any additional constraints in your mechanical system by selecting the appropriate joint from Motion menu by selecting Joints, or by right-clicking the constraints node in the IntelliMotion Browser and then selecting the SolidWorks components that you want to constrain. Learn to create constraints
Define motion drivers to drive joints in your mechanical system. Not all joints have motions applied to them. Learn how to create joint motions and motion on parts.
Optionally, define gravitational force, springs, dampers, or other loads acting on your mechanism. Learn to create forces