How I get the "preview" window on the far right hand side to minimize or disappear?
so that the class extends fully to the right hand side.
If this is really a window added by NetBeans (which I doubt, it doesn't look native to me) then you can click on it to select it, then press control-w (close current window/pane).
However, this looks more like something a plugin has added. You can try control-shift-enter (show only editor) and then again to switch back. If that doesn't work then you should go over your plugins to see what added this.