Since you have asked questions that seem to be oriented towards graduate level research in the past, I will answer on that level.
In interview research, there is a technique called the "snowball" method of finding people to interview on a given subject. You identify a few people you know you should interview and then you ask them at the end of their interview for names of other people you should interview. You can do a similar thing for finding articles that might be relevant to your research.
The way to start is with readings that you have done for class or for your comprehensive exams if you've gotten to that point. Identify ones that seem to be of interest. Look at the works that they cite. Go to those works or other works by the same author. If you find those useful, look at what they cite and so on. In addition, when you find articles that are useful to you, look them up on some database like ProQuest. Look at the keywords that are assigned to them and search for other articles that have the same keywords.