Method One: Bing webmaster tools provides an XML file that can be uploaded into the root directory of the website to verify ownership. To use this method, download the XML file provided to you in the dashboard, and upload it to your website via FTP. Once it has been uploaded to the server, you can go back to Bing webmaster tools and see that it will run a verification process.
Method Two: If you would rather not upload an XML file to your root directory, you can use the META tag verification method. Simply copy the META tag from the webmaster tools screen and paste into the header of your index page on your website. Once up update the page on the server, you can go back to Bing webmaster tools and see that it will run a verification process.