You can host your photos on photobucket (it's free). Just start an account there, and use the bulk uploader tool to upload the pics from your computer, as it is much easier than uploading individually, even if you only have one to upload. Once you have uploaded the pics, resize them so that the picture will be the right size for the screen here, 480 x 640 seems to be a good size. Then you can copy and paste the image code, which will be provided there on the site, the one that begins and ends with img, into your post, and it should appear!
One note, even after you resize it, it may still look too big to you after you post it, but after a day or so you'll see it in the right size. To everyone else, the correct size will show up immediately.
