how do I suggest an image be my primary

I need to change the primary image on our episode page. I appreciate any help you can give me. 

The current primary image has this message on it: 

"This is already the primary image. To suggest a new primary, please select a different image to replace it."

How do I select a different image to replace it? 

I have a second image on this episode page, and need to make it the primary image. How do I do that? 

The episode is Four Died Trying 0: The Prologue

Here is the episode page: 

https://www.imdb.com/title/tt30275691/?ref_=tt_mv_close

Link to what we want to be the primary image: 

https://www.imdb.com/title/tt30275691/mediaviewer/rm3893721857/

Link to current primary image that we ultimately want removed from the episode page: 

https://www.imdb.com/title/tt30275691/mediaviewer/rm1394166273/