I have been doing the same Reuse and Modify External CAD Data tutorial since 2 days but it's the same. In my licensed CATIA Assembly Design app I could not find the option "Insert an existing 3D part" but in the tutorial the option is being shown to complete assembly. But its not the case for me. Is learning material outdated? Is there any way to get around it and do the assembly? below are the screen recordings of the problem im facing: