Well, that depends a lot on what you mean specifically by "style." A CSS? A specific design? Or maybe just a color scheme you want to incorporate?
There are several different options you can use to make a UBB very similar to an existing web site design, including using tables around the UBB (in the header and footer) to add site navigation, logos, and more.
Tell us a little more and someone can probably give you a more exact answer. <img src="https://www.ubbcentral.com/boards/images/graemlins/smile.gif" alt="" />
-jlb