Are you using SFML to visualize the red-black tree? Do you already have a working red-black tree algorithm set up? I think if you have some kind of Node class, you could use that to inherit from sf::CircleShape. You would have to use the sf::RenderWindow, and then you might want to look at it like a grid because you'll have to specify where to draw the nodes. Maybe you could store all the points in a VertexArray, and then draw the nodes at the respective points. You would want to create methods in the appropriate insert / delete RB-tree operations that use the setPosition(x, y) function from sf::CircleShape.
Naturally, it would help if you specify more about what you need to do and what you've already done?