Customize the form layout

Hi, I try to adjust the layout of the form in visual-form-builder.css. But whatever I change, the effect is zero. I followed the instructions on http://vfbpro.com/2012/11/15/visual-form-builder-pro-customizing-the-form-design/ . Does that only work in the pro-version?
For instance: I want to make the background transparant and reduce the vertical distance between the lines and blocks. Does anybody know what I do wrong? I use the free version. Vincent

https://ww.wp.xz.cn/plugins/visual-form-builder/