This XML file adds a search button for YouTube in GNOME 3.
To install you need to download the YouTube XML file, move it to
/usr/share/gnome-shell/search_providers/ and restart the gnome shell.
This can be done easily via the terminal with:
sudo mv youtube.xml /usr/share/gnome-shell/search_providers/
Finally you need to restart the gnome shell by using ALT+F2 and entering
How to search in Gnome 3
If you aren’t familiar with how to search using Gnome 3 then here’s a brief overview. First of all you need to enter the Activities Overview by either moving your mouse cursor to the top left of the screen, clicking Activities in the top left of the screen or by using the special key.
Once you are in “Activites mode” you can start typing your search query straight away. At the bottom of the screen are buttons of search providers you can use which, by default, includes Google and Wikipedia. If the default search provider, which is highlighted, is what you want to use you can just hit enter instead of clicking a button.