There is no install, you just upload CSS file to your web server and tell the HTML/XHTML/PHP or what ever format you gone use that it should use this layout, plus in the document you tell tags which settings to use. For example
<table class="bordless"....> . If image is used as background or in some decoration, find it CSS and change the path of the image for the path to your image
No installing Business :)
Just upload the files and make sure the paths are correct and work on the images
You have to write your web page code to use the styles that are there.