Need help figuring out how to properly scale image to rectangle

I'm new to UI/UX design, and I'm trying to figure out why the full movie poster on the right can't seem to properly, cleanly, fit into the rectangle when I try to drag and drop. I've been Googling for multiple hours, and I can't seem to find a proper answer. I assume it has something to do with aspect ratios, but when I tried adjusting the poster in Canva to a 'Landscape', it still couldn't fit inside the rectangle without some aspects being cropped or the image quality looking atrocious.
Would love for some support 🙂
