User blog comment:Nkstjoa/Top 8 Completed What-If? Death Battle's poll/@comment-26959187-20141213105428/@comment-5035900-20141214010736

Not sure if you can on mobile, but if you can get to a computer, all you have to do is click on the upper right on Contribute, scroll down to Create a Page, title it after your desired What-If? Death Battle, and the rest is up to you.

Just be sure to check if there's already a page for your battle and keep to the Wiki's rules of no rematches (ex. Mario VS Sonic with more power-ups).