To embed a url in a post, surround the url with [ url ] h t t p://www.test.com [ /url ]. To place a url link under text [searchengineworld.com], use [ url= h t t p://theurl.com]title text [ /url ].
(no spaces in the above examples of course). More examples on the help page [webmasterworld.com] linked at the top of every page.