1) Are you posting it as a file where people have to click to see it or where it's visible along with text? The problems I've heard have been when posting a file. Also I had a problem uploading a file as a JPG, but when I resaved it, it uploaded, and it also uploaded as a PNG. What kind of file were you trying to upload?
2) On the homepage under "Autograph Live Notes" you can see how to post images visible and with text.