You can add sitemap to Yahoo via Yahoo Siteexplorer Basic principle to create sitemap - How do I make a Sitemap? - Yahoo! Small Business Help Instruction to submit sitemap both Google and Yahoo - Submitting your Sitemap file to Search Engines - Yahoo! Small Business Help
A Quick question Once u submit the sitemap do yahoo auto check it for future changes in the sitemap or i have to update the sitemap regularly
There is also the possibility of mentioning your web Sitemap URL in your Robots.txt file and then all search engines would find the file and scan the URLs.
Yahoo follows a similar approach to Google. Again, there is a dedicated sevice for webmasters (Yahoo! Site Explorer) and a procedure for verifying your ownsership of the site. First go to: siteexplorer.search.yahoo.com/ Add a site, then click on the verification button. You can then download a verfication key html file - which you will need to upload to the root directory of your webserver. Then you can return to Site Explorer and tell Yahoo to start authentication. This will take up to 24 hours. At the same time you can also add your sitemap by clicking on the manage button and then adding the sitemap as a feed.