Missing "Extensions" in "Window" drop down list

Hello, All,
I’m using SketchUp 2017.
When trying to install / open a plug-in, in the top Toolbar, I’m directed to Window>Preferences>Extensions>etc.
But I there is no “Extensions” in “Preferences”.
What am I doing wrong ?

Extension Manager has replaced it in SU 2017, on Window menu.

You can Install, enable or disable extensions from there, and Update or Uninstall them via the Manage tab .

Thank you John, you’re a gentleman.
This is coming from someone with the mind of a flea, so don’t get a big head !
Jim … :-S