I am using Ubuntu 13.04. In which I have Libre Office Writer. I want to know which the version currently installed. What is the way? Where to look for?
Open any of the LibO applications, then choose Help > About LibreOffice from the toolbar. That should tell you what you want to know.
If you didn’t mess with LibreOffice installation then you have 4.0.x version. See details: http://packages.ubuntu.com/search?suite=raring§ion=all&arch=any&keywords=libreoffice&searchon=names
But just in case if you ask another question: “How to install LibreOffice 4.1.x on Ubuntu 13.04?” Then see the following post: Will the current libre office 4.0.2.2 on ubuntu be updated?