Articles come in many forms. Newspaper articles, which you may have researched while finding primary sources, are often primary sources. Magazine and journal articles are typically secondary sources, and they are great to reference when you are researching. Some magazine and journal articles muight be art gallery reviews. Depending on when they were written, they may be primary sources, too.
It is best to wait to search for articles after you've done quite a bit of research on background information and in books. By now, you'll have a better idea of what you are looking for.