When you start Autodesk Navisworks, a new “Untitled” Autodesk Navisworks file is automatically created for you. The new file uses default settings defined in the Options Editor, and in the File Options dialog box. You can customize these settings, as necessary.
If you have a Autodesk Navisworks file already open, and want to close it and create another file, click New 
on the Quick Access toolbar.