How to separate geometries such as wheels?

I noticed the Ferrari that comes with JME3 test data has the wheels in separate geometries. Within the fancy car demo it references these geometries as WheelBackLeft for example although looking in the scene composer it is named back_left. Although the Ferrari folder holds WheelBackLeft.mesh.xml I dont think it does anything since its not in the j3o format.
How could I create wheels that I can use just as they are used in the Ferrari model in my own model? How would I know what name to access them with? I use blender (and am in no way good at it).

Just name the nodes in blender (upper right) thats it, then after importing you can get them by the name.

Your best bet is to open the scene inside the SDK once you have converted it to a j3o and use the scene explorer to check what everything is called.