I know that it's a very simple procedure, anyway each Office version has a little different menu to access Out Of Office link/Tab.
On this blog I proceed to copy and past two link that, easily explains how to enable Outlook OOO on organization with or without Exchange:
How to Set Out of Office (Auto Reply) in Outlook 2003, 2007, 2010 and 2013
The following instruction is fit for Outlook 2003 and 2007. It is also fit for Outlook 2010 and 2013 without Exchange Server. If your email account is connecting to Microsoft Exchange Server, please
http://www.addintools.com/documents/outlook/howto-out-of-office.html
How to Set Out of Office (Auto Reply) in Outlook 2003, 2007, 2010 and 2013
The following instruction is fit for Outlook 2003 and 2007. It is also fit for Outlook 2010 and 2013 with Exchange Server.
http://www.extendoffice.com/documents/outlook/484-outlook-2010-how-to-set-out-of-office-in-outlook-2010.html