it's probably a clip that you need to pop out with a tool or a rag.
that's how most of the american cars do it.
take a rag, and shimmy it back and forth in between the door card and the crank, while the crank is pointed up, toward the window, and the clip should pop off, then the handle just comes right off.
if there isnt a screw there should be a spring loaded clip just behind the base, they actually make a special tool for this but u can use a flathead screwdriver to push down the clips...you'll have to push the panel inward and turn the crank until you can see these little clips, just push the crank out of the clips and you should be good...