Configure Body blocks. Click the Body blocks to open their dialog boxes; specify their mass properties (masses and moments of inertia), then position and orient the Bodies and Grounds relative to the World coordinate system (CS) or to other CSs. You set up Body CSs here.
Configure Joint blocks. Click each of the Joint blocks to open its dialog box and set translation and rotation axes and spherical pivot points.
Select, connect, and configure Constraint and Driver blocks. From the Constraints & Drivers library, drag, drop, and connect Constraint and Driver blocks in between pairs of Body blocks. Open and configure each Constraint/Driver's dialog box to restrict or drive the relative motion between the two respective bodies of each constrained/driven pair.
Select, connect, and configure Actuator and Sensor blocks. From the Sensors & Actuators library, drag and drop the Actuator and Sensor blocks that you need to impart and sense motion. Reconfigure Body, Joint, and Constraint/Driver blocks to accept Sensor and Actuator connections. Connect Sensor and Actuator blocks. Specify control signals (applied forces/torques or motions) through Actuators and measure motions through Sensors.
Actuator and Sensor blocks connect SimMechanics blocks to normal Simulink blocks. You cannot connect SimMechanics blocks to regular Simulink blocks otherwise. Actuator blocks take inport signals from normal Simulink blocks (for example, from the Simulink Sources library) to actuate motion. Sensor block output ports generate Simulink signals that you can feed to normal Simulink blocks (for example, from the Simulink Sinks library).
In the most straightforward case, you apply forces/torques and initial conditions, then start the simulation in the Forward Dynamics mode to obtain the resulting motions. In the Kinematics and Inverse Dynamics modes, you apply motions to all independent degrees of freedom. With these modes, you can find the forces/torques needed to produce these imposed motions.
Encapsulate subsystems. Systems made from SimMechanics blocks can function as subsystems of larger models, like subsystems in normal Simulink models. You can connect an entire SimMechanics model as a subsystem to a larger model by using the Connection Port block in the Utilities library.