If you can't see the Insert panel, go to the Window menu, and select Insert.
I go to the Window menu ("ventana" in Spanish) and selected "Insert" (it adds or deletes a checkmark) and this has no effect on the right hand side, where my panels appear. It has an effect on the top bars, where I see the tabs: "Coomon", "Design", "Forms", etc. I can see the "div" element at the "Common" and "Design" tabs. But I cannot find the "Header" item, as instructed in the video.
I am using the "Classic" display.
Please help me!
If you are using the Classic display, you're using Dreamweaver CS6 or earlier. The Classic display doesn't exist in Dreamweaver CC.
Since you have Creative Cloud, you should be able to download and install Dreamweaver CC. Both versions can exist on the same machine (although they can't be used simultaneously).