Microsoft Merchant Center is a platform that allows you to create a product feed - this contains the necessary information needed for your store's products to show up in the Microsoft Search Network.
To create a Microsoft Merchant Center:
On the top menu, click Tool.
Click Microsoft Merchant Center.
Click Create store.
Enter your store info, including your Store description and SSL Checkout selection.
You will then be asked to verify your site through Domain validation, through either
Bing Webmaster Tools
Click Save.
For more information, you can read Microsoft's help article here: https://help.ads.microsoft.com/apex/index/3/en/60048