Measure the poster, measure the frame. One of them is not 36 x 54. What you probably did wrong was to not verify the size of the poster before buying the frame.

I bought a dead pool poster (marvel super hero) and it is a 36 x 54 poster. I was like 60$ but to have the company frame it is would have cost me 150$ dollars more.

So I bought a 36 x 54 picture frame. It had a lost of extra space in it and I haven't a clue what i did wrong.....

any suggestions