Follow these detailed steps to obtain and install the correct version of Subassembly Composer.

Subassembly Composer is a powerful tool that allows users to create and manage subassemblies in Civil 3D. A subassembly is a collection of parts that work together to form a single component, such as a curb, gutter, or sidewalk. Subassembly Composer provides a graphical interface for creating and editing subassemblies, making it easier to design and manage complex infrastructure projects.

When installing Civil 3D for the first time, you must ensure the Subassembly Composer box is checked: Run the Civil 3D installer from your Autodesk Account. Navigate to the section.