Here is a guide to install Liferea feed reader on Ubuntu 13.04, you can install Liferea using the Ubuntu Software Center.
Liferea is a simple FeedReader clone for GNOME. It is a reader for RSS/RDF feeds which also supports CDF channels, Atom/Echo/PIE feeds and OCS directories. Liferea is an abbreviation for Linux Feed Reader. Visit the Liferea Homepage.
To install Liferea click on the link below
When the software center is opened click on the Install button and enter your password to authenticate the installation. When Liferea is installed you can close the software center, to start Liferea press the SuperKey and type: liferea
How to open the apt link? Read this article.