These sites are for folks who are buying or selling something. These service sites will register your site for you, at a cost. The sites in are listed in alphabetical order in their respective categories. Some search services categoriize web pages and will allow you to register in only a small portion of them, some may only allow you to register under a couple of categories. The best way to determine which category your page best fits in could be to check out the site and find out which category best fits your service.
Some search services require a list of keywords or a description or both.
Choose these carefully and make sure they include everything your service provides. In a few days their service will come in and check out your front page, and your Title. It is important to list as many keywords or descriptions of your site on your front page. But don't keep repeating keywords over and over, many search engines will disregard all information when this situation is encountered. For best reults, you should perform a careful, methodic registration at each service.