I'm not exactly sure if this is what is being asked here, but I'll give it a try:
When you upload a picture to the image hosting portion of this website, you get a page that looks like this:
You need SOME of the text on the third line of code in the list of four. Copy ONLY the URL of the image - not the HTML code. For example, using my example page above, you want to copy just the "http://imghst.gpsfiledepot.com/1332296046.jpg
1) go to the page where your can edit your download page
2) position your cursor where you want the image
3) click on the little picture frame button in the middle of the second row of toolbar buttons
4) A dialog box opens...under the URL field, paste the URL of your image.
5) No need to populate anything else in that dialog box
6) Click OK and you're done!
There are other ways to do it, and if you're still not sure how to do it, I can add some better instructions.