You can import many 3D components into SOLIDWORKS, or you can create them. When you have the component you need, add connection and route points to it, and add the part to the Component library.
Most suppliers can supply either 3D models or dimensioned drawings of
components. In many cases you can import the 3D models directly into SOLIDWORKS. If not, you
may need to model them. Once you have the model, add CPoints or RPoints as needed.