You may already have an idea for a topic from the course material. Or you may need to do a bit of brainstorming. To help generate ideas for a topic, you may wish to look at some magazines such as Psychology Today. These can help you get started by doing some general reading on topics related to Psychology - but they would not be considered primary resources.
For example, I did some reading in Psychology Today on autism spectrum disorder (ASD), and came across an article that discusses how girls are less likely to be diagnosed with ASD than boys. The article mentions a recent study on how girls use social language more than boys, and how that may impact on the lower rate of diagnosis. I could then use this study as the starting point for a New Discovery article.