Actually, I'm trying to add some extension to my Ubuntu GNOME, but it is showing some error when I'm trying.
The issue is like:
"Although the GNOME Shell integration extension is running, the native host connector is not detected. Refer to documentation for instructions about installing the connector."
It sounds like you might be using Google Chrome, which needs a special extension to use the website. In Ubuntu the package is called chrome-gnome-shell.
If you're using Mozilla Firefox you can get an extension from the Firefox Addons site, although I've read on OMG! Ubuntu that the Chrome extension works for Firefox as well.