I'm a bit confused as to what you're asking. The word "Search" is a direct link to the search.php page. I used CSS to make it not really look like a link, but it's just a standard hyperlink. The search field is in a simple form which calls the search.php page. If you are running a vBulletin board, you could put the following wherever you want:
Then, just play around with CSS to make it look the way you want :) Notice that when you do a search, a list of threads is returned. If you change the showposts attribute to 1, a list of individual posts will be returned. Your preference :)
Also, since it's just a regular ol' form - that HTML code can go anywhere ... within a vBulletin template or on a regular HTML page.