Citation managers help you keep track of all of your sources (some will even save copies of articles). No more forgetting authors or losing all the information you've found when you lost a notebook.
They also make it easy to cite your sources for your papers. Many citation managers have word processor plug-ins that make it easy to cite in your papers. Using what you have cited in your paper, they can genereate your Works Cited/Reference List. And they will do it in the common citation style of your choice. Which means you don't have to put all of your resources in APA style (though you should check them to make sure the style is current).
There are a variety of citation managers you can choose.
To create your free accounts, go to their respective websites on campus or using a method of database remote access.
Which one should you use?
Check out this in-depth comparison of many citation managers from Wikipedia.