There are many ways to find data. Here are a few possibilities to start out with:
Once you find your data, make sure that it fits your need. It often isn't possible to find the perfect data set with all the variables measured exactly how you'd like them, but there are certain measures that you will most likely need if you're studying a particular topic. Think about the year the data was collected, and whether the data is recent enough. Think about whether the data is relevant to your topic and whether the variables measure what you intend them to measure. What is the sample size? Does your data need to be longitudinal? If you can't figure out certain details about the data that are important to you, contact the data creator.