The Office 2010 suite that includes Microsoft Publisher is Microsoft Office Professional 2010. Is this the Office suite you installed? If you installed Microsoft Office Home and Student 2010 or Office Home and Business 2010, your Office 2010 suite doesn't include the Publisher application and will, by default, install a trial version of Publisher 2010 instead. To use the full version of Publisher 2010, you'll have to buy it separately.
Learn more about which applications are included in each suite of Office 2010 here:
Which Microsoft Office 2010 suite is right for you?
You can also get help from the Microsoft Community online community, search for more information on Microsoft Support or Office Help and How To, or learn more about Microsoft Assisted Support options.