Assume your horizon is deployed in /opt/stack/horizon/
Follow the commands below:
$ visualizations# ls
dashboard.py flocking __init__.py README.rst settings.py static templates
$ mv settings.py /opt/stack/horizon/openstack_dashboard/
$ cd ..
$ ls
visualizations
$ mv visualizations /opt/stack/horizon/openstack_dashboard/dashboards/
$ service apache2 restart
Then you can see the added new dashboards.