If you have a yahoo address, flickr is the easiest. you just type in your yahoo address and fill out a couple of things and you're on flickr. If you don't have a yahoo address, it's a bit longer.
Once you have the account you need to upload your picture. It's idiot proof just follow the "Upload pictures" link.
Then go to the photo page. You need to find the url. On flickr you click on the "all sizes" button above the picture.
On the bottom of that page you'll see a field marked "Grab the photo's URL". Take the link out of that and paste it in the box across from where it says "I have my own pic" on the Escape artists profile modification page.
Have fun