Hi Sondra. As far as I’m concerned, you’re free to use the main poster so long as you credit the film, the production company/distributor behind it and state that it is promotional material. If you’re reviewing the film, which you are, Fair Use would suggest that using a poster to discuss a film is okay. A would-be viewer of a film is very unlikely to use a review featuring a poster as an alternative to seeing the film itself is the basic idea :)
So it should be all good!

I’ll look forward to your review! Thank you for checking this with me, too.