Replacing Primary Image

Hello, I'm struggling to replace the primary image on my project as I initially set the wrong poster for the primary and not sure how to swap it out. Heres' the title: https://www.imdb.com/title/tt42369871/

The current primary is an off-center AMC poster but I'd like to swap it for the green "special look" poster, which is what it should be. Would appreciate any help, thanks!