Where to insert a css code

[baby41]

This is not a product or plugin just a CSS Popup Image Viewer. Here is a simple description:

"Enable arbitrary links or image thumbnails to pop up an enlarged (different) image onMouseover by using this CSS code. With the help of CSS's ":hover" pseudo class, combined with relative and absolute positioning, the enlarged images are simply included on the page as normal HTML, "popping" up on demand. CSS is behaving more and more like scripting!"

My question is:

Can I insert this code to my Vbulletin forum and where.