From the parts breakdown, it lists the handle as a complete assembly, and then the subcomponents, one of which is center cap. Most of these have a cap that pops off to expose the screw which holds things together. It appears that yours is fairly standard in that manner. See if you can find a seam between the top of the handle and the rest of it. Being careful to avoid scratching things up, pry the cap off. You should see the screw, which will allow the rest of the handle to be removed. Should be easy from there.