Can you provide more information about the problem you are trying to solve?
From the right side tool bar you can create a Spring element, which is an idealization used for structures in your model (assembly) that provide stiffness or flexibility without significant mass (inertial) effects. When you create the spring, you have to specify the Properties, which include the stiffness constant. If you have an Advanced license of Mechanica, you can specify a stiffness matrix for tensional and torsional stiffness relative to a specified coordinate system.