In Autodesk Inventor, Help is accessed from Environments. Click Autodesk Nastran In-CAD
icon. The Autodesk Nastran Ribbon opens up. Now, click on Help button under Nastran Support panel.
For Context Specific Help, click on the question mark in any of the toolbars to open the Autodesk Nastran In-CAD User's Guide directly to the section you are currently working in.
In SolidWorks, click on Help – Autodesk Nastran In-CAD Help to open the default page.