First download the latest lens package from the project launchpad page @ launchpad.net/unity-lens-bliss (the green button to the right)
Move this package to your Home folder. Right-click on it and choose ‘Extract here’.
Next open a terminal and enter the following commands: -
The lens is now installed, but you will need to log out and back in for it to become active in the Dash.
If you decide you don’t like it, or don’t want it cluttering up your Lens bar, it can easily be removed by opening deleting the ‘unity-lens-bliss’ folder in /usr/share, and the ‘bliss’ folder in /usr/share/unity/lenses.