How can I type a review for a podcasts on the podcasts app?

I have reviewed podcasts that I have really liked before, not by episode, but by podcast. I have tried typing reviews for podcasts that I have recently started listening to, to which I am subscribed, but I can't find where to place a review. I even searched for the podcast, on the podcasts app and I can see reviews that others have made, but there is nowhere for me to start writing one. I am using an iPad.