Do lots of research on it, from several sources. Although be very, very careful not to plagarise or copy from any of those sources.

Analyze: Think about this sculpture both in terms of how we see it, today, and why it was important back when it was created. Was it in some way revolutionary back then? Why? Was it somehow different from other things the artist had done? Why? Is it somehow related to another artist’s work? How? Why do you think that? Does the piece have an obvious meaning, or one that you interpret? Why do you think that? Is the sculpture popular, or not. Why?

Your analysis is what you end up arguing about. For every question I put, above, I then asked “Why?” The reasons why you think that are your argument. I wouldn’t pick every question I asked, above, but you’d want to find one core question or two that you feel exemplify this piece to you, and use that.

If you say that (this isn’t suppose to be true, btw, just an example), the Thinker is the best example of sculpture since sliced bread, you need to say why you think that, and then back that up. That’s your argument.