Read this carefully. Either your pixel size is too large OR the size in KB's is too large, even if the pixels are reduced. First save your image as a gif., no bitmaps or tifs or other giganitic file. Go to Irfan View , or like software... Irfan View is a free download... and reduce the size of the image to a usable size if need be. This is what the instructions say in your profile page.
Displays a small graphic image below your details in posts. Only one image can be displayed at a time, its width can be no greater than 100 pixels, the height no greater than 100 pixels, and the file size no more than 64 KB.