You can look through the JFreeChart demo that is included with the FXGraphics2D download. Here is a link to the source file:https://github.com/jfree/fxgraphics2d/b ... Demo1.java
You'll see at line 70 that there is a very basic ChartCanvas class that extends Canvas and is therefore a Node. You can place that anywhere in your JavaFX UI. The role of FXGraphics2D is *within* that chart canvas, to translate the JFreeChart drawing calls (which use the Graphics2D API) to the equivalent JavaFX Canvas rendering.
When I have time I plan to create a more full-featured ChartCanvas that supports some of the features that are found in the existing ChartPanel class that you can use in a Swing UI. This has been done for the Orson Charts viewer, but I didn't get to the JFreeChart one yet.