How do I upload a GIF or image with my answer on Tumblr?

So I get a message(a question in other words). And I want to answer with a GIF or an image. But on mine I don’t get ”+ Upload Photo” I get the little picture of a tree that you click on and I get “Image URL” and “Image Description”. So I click and drag my photo to my browser and copy and paste the URL. But when I post it I get a clear box, so I click on it. And. There’s. No. Picture. Help?