How do I install GNOME Shell extensions?
Manage Gnome and the shell extension
The GNOME extension aren't in official repository so you can use a PPA where you can download all of them;
These are a set of gnome shell extension :
Thx to http://www.webupd8.org/ for it PPA.
see this gnome-shell page-> https://live.gnome.org/GnomeShell/CheatSheet
The GNOME website has an Extensions section set up, which is currently in its Beta phase. It promises easy installation of extensions, and management of installed ones, through a web interface.
The site can be accessed here: https://extensions.gnome.org/
Gnome-shell extensions can be installed from the Gnome-shell extensions web page. The site is: https://extensions.gnome.org/
To install an extension click on the extension and then you will go a page describing the extension.
In that page you can see a slider switch. Turn on the slider if you want to install the extension. Then you will see a prompt to install the extension.
The installed extensions can be managed from https://extensions.gnome.org/local/
1. Go to the gnome-shell extensions page using a supported browser (that is not totally secured to anything running on or coming from the web).
Like the stock gnome-browser or a clean install of firefox should work as well. I sometimes had issues installing extensions using google-chrome or midori.
2. Filter by "Supported by: Current Version"
3. Click the toggle-Button of the Extension you want
4. A "install this extension"-question should pop up. Confirm.
(5.) In rare cases you need to reload the gnome-shell to make a new extension work without issues. (RARE!) - open the gnome-shell run dialogue (Alt+F2 ? - if not set check Alt+F2 doesn't display the Run Command Prompt in GNOME Shell), type in "r" without quotes and hit [Enter].
I have been going crazy trying to get this to work on a clean installation of ubuntu gnome 14.04. I have found the solution. Open firefix. Go to the addons. Under the plugins, you will see Gnome Shell Integration. Select that and change the activation options to ALWAYS ACTIVATE. I then closed out firefox and then reopened. When I went back to addons.mozilla.org. I was able to install the extenstions (The slider stayed in the on position. The extenstion did show up in the tweak tool after that. I hope this helps. I have read so many answers and tried so many things. I am just happy that I figured it out and I'm able to share it with everyone. Here is quick list of versions so you can verify against yours.
Clean install of Ubuntu Gnome 14.04 Firefox 34. Version that was installed during installation.