Step 1.) http://www.netstumbler.org/search.php. It's at the very top of the page between FAQ and New Posts.
Step 2.) Enter keyword(s). The keywords have to be at least 4 letters long. Think of what it is you're wanting to find, and pick some specific keywords. If you have a router, search for the word 'router' or even try searching for the router's manufacturer's name, such as 'linksys' or 'netgear'. If you're unsure of what to search ...