Log into your Bing Webmaster account and then open the following URL. Replace "yourwebsite.com" with your domain name and remove the space between '/ / ' in the URL.
https:/ /www.bing.com/webmasters/home?siteUrl=https:/ /www.yourwebsite.com/&state=verifySite
It should show you all the verification methods. You can get the verification code from that page.