Cannot Access Revit Extention

[Anonymous]

I am a student using Revit 2016. I have seen videos (Revit 2015 used) about the Revit Extention but cannot seem to find it on the ribbon menu. I found an update that I thought might be the Extention upgrade but it dis not change the menus. I also found the actual Revit Exention link but the download link did not show up. I just don't understand because on the video the Extention button shows up on the menu bar. Any ideas?

Thanks 

[RDAOU]

@Anonymous Hi

1. which build of Revit 2016 are u using? Is it updated (at least till 2016 R2)?
2. did you download the REX2016 installer?? is it THIS ONE HERE? Or which link was it that you found?
3. Last; you might need to reset the user interface. Simply, with revit closed, you can delete the UIState.dat file located in the following folder:

%APPDATA%\Autodesk\Revit\Autodesk Revit 2016