To install Deco, add plone.app.deco to your buildout and install the Deco extension profile into a Plone site. This will install:
To test it, add an item of the newly installed Deco Page type to your site.
Note that Deco and plone.app.toolbar significantly affect the way a Plone site is used and operates. You should take care if installing on an existing site and test carefully.