Exporting to a part is currently unsupported. Please see the next tutorial about exporting assemblies. This tutorial describes the very simple process for exporting a SolidWorks part to a URDF.

This tutorial covers the process of exporting a SolidWorks Assembly to URDF using the SolidWorks to URDF Exporter

This tutorial covers how to organize your SolidWorks assembly to create a better workflow and also how to reduce the exported mesh complexity when dealing with complicated assemblies.