help question about transparancy background

Hello,

I need to build this site: http://wp1.bewustzijninwording.nl/ in upfront.

The homepage needs an other background (the peacock), and the green boxes should be white transparance. So how do I get a white textbox with background color opacity of 70 %. And I want also a button in it and the second e-book part with an image and button.

Can you please say how I do that. I’m building the new site in upfront on this domain: http://maaike.cherallontwikkeling.nl/