In a terminal, type the following:
sudo add-apt-repository ppa:remi.rerolle/unity-lens-tomboy sudo aptitude update sudo aptitude install unity-lens-tomboy
The log off and back in. The lens should now be available from the Dash
Open the Dash, then start typing something. The matching Tomboy notes will be listed in a dedicated section.
You can also click the Tomboy icon in the list of available lenses. From the Tomboy lens, you can also enter a search term, and use the filter buttons to limit your search to some notebooks, or based on modification time.
The lens is also compatible with GNote. Please bear in mind that this has been roughly tested. Do not hesitate to file issues if anything goes wrong while using GNote instead of Tomboy.