Open access journals are free journals (don't require a subscription) and provide immediate, online access to the results of scholarly research. Some are peer-reviewed, some are not. Some are predatory. Make sure to evaluate any publications or articles you might find for free online.
Use Google Scholar to help you discover other scholarly items. You won't be able to access some of the articles, but if there's a promising title or an article you'd like to pursue further, you can check to see if we subscribe to that journal. If it's not something we have, we can try to get from another library.
In psychology, the most common kinds of articles are literature reviews and experimental reports. These Purdue OWL links give a short overview. See the APA Manual and your textbook for more information.