YaHoo is using Bing for their search engine. So YaHoo is actually Bing, what you see on Bing you also see on YaHoo.
Bing has their own Webmaster Tools service, something similar to Google Webmaster Tools.
You can access their page from here: http://www.bing.com/toolbox/webmaster/?lc=1033.
Create an account from there, “Sign up with Microsoft Account”.
Add the url of your website > verify it > Configure my site > sitemaps.
If you don’t know how to create an XML sitemap, check this previous article.
The sitemap presented there works for Google and Bing (YaHoo).
To see what pages are indexed in Bing, YaHoo and Google, write “site:yourwebsite.com” in their search bar.