Sticky background

I’m pretty new to wordpress so I decided to use a premade template called pointspace instead of making my own. The thing is that the css is written in the style.php file instead of the style.css

I tried this code in the style.php file
body { font: normal 62.8%/1.3 <?php echo $pointspace_body_font; ?>; background: #000 url('images/<?php echo $pointspace_body_bg; ?>'); color: #<?php echo $pointspace_font_color; ?>; background-attachment: scroll; padding: 0px 0; }

The function.php file also contains this code about the background

array(    "name" => "Body BG image<br /> <small><small>Can be of any size, it will be repeated in both x and Y axis <br />(Refer to current images for idea! Image should be placed within images folder of theme.)</small></small>",
            "id" => $shortname."_body_bg",
            "std" => "bg.gif",
            "type" => "text"),