The extension in 'Shell OSD' is outdated, and does not seem to work with 3.6+. A alternative extension that can be used is 'Panel OSD', which is more up-to-date, and should work with Gnome Shell 3.10+.
By default it shows the notifications on the top of the screen in the middle - using the settings (these can be opened from the extension's webpage or Gnome Tweak Tool) this can be changed to be on the top right:
The version for 3.10+ can be downloaded and installed from here
The 3.16 update removed compatibility with versions older than 3.10 - if you have a older version, you might be able to install it with:
cd ~ && git clone git://github.com/jenslody/gnome-shell-extension-panel-osd.git git checkout d2289c2569d127725522eaa385b175220b28514c cd ~/gnome-shell-extension-panel-osd ./autogen.sh && make local-install
I haven't tested this, but basically all you should need to do is get a version before this commit which removed the compatibility. Sources: extension README, https://stackoverflow.com/a/7832839/2943276