Nikon Flash pop-up post using Speedlite YONUGNUO

Nion D7100, I can not use any of the settings and access the menu message last night with my YONGNUO speedlite. When I turn it on, the camera's flash pops up and the viewfinder only displays the left area with the flash symbol in the corner. Tried a set to the factory settings but it would not be reset, options?