The bibliography and notes section of a Wikipedia article can help you locate more sources on your topic.
Just make sure they are real citations!
Which of the online reference sources listed above is available to everyone, without a subscription?
The Heilbrunn Timeline of Art History is published by the Metropolitan Museum of Art in New York and is free to all.
You must put all the background sources you use in your bibliography.
Nope, you don't have to since it's really just to learn enough to ask good questions and figure out where to go next.