[ubuntu] Setting automatic updates

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http://ubuntuforums.org – I'm using Ubuntu 12.04. I am new at Ubuntu. The system has given me a message that says "you must check updates manually" ... "You can configure this behavior in Software Sources on the Updates tab". But I can't find Software Sources. I tried Ubuntu Software Center but that doesn't have an Updates tab or anything I can see relating to automatic updates. Does anyone know how to setup automatic updates? (Hardware)