Where is the "Extensions" menu?

I just installed SU 2016. It doesn’t have an extensions menu. How do I install extensions?
How do I find them (before and after installed)?
How do I get the SketcUcation extension manager?

Hi i have the same problem:

i can’t find this menu:

If you haven’t installed any plugins, the menu is hidden but will be visible after the installation of the first plugin with an item in that menu.

e.g.
https://help.sketchup.com/en/article/3000263

What do you see instead?

ok thanks, i have just to install and it will be, thanks i understand