Hi Patrick,
when you generate the Data service project in WebRatio Cummunity Edition the related application will be deployed on WebRatio free Cloud Account.
If you want to sync the Domain Model of the Mobile project with the data service, the "Back-end Base URL" property should refer to the data service application running on Cloud (e.g. http://freexxxxx-freeapp.eu.webratio.net where xxxxx is the id of your free Cloud account).
To manage database connection please refer to this guide: http://my.webratio.com//learn/learningobject/webratio-cloud-dashboard-user-guide