Follow the upgrade steps as you normally do above. You will also need to follow item #8 under Setup, to add the database configuration.
You can check that everything is functioning by going to the upgrade advisor http://your-instance/upgrade-advisor.php
If you need to re-import your data from your root server you can run the following script. This will delete any changes you have made since you upgraded.
TRUNCATE TABLE config;
DELETE FROM flags WHERE flag_name='root_server_data_migration';