If they are asking for a URL then you have got to find somebody else to actully store the photo on the web.

If your ISP provides free web space then you could use that although you will probably need to download some FTP software.

There are a number of companies who will host photos for you, I use Bravenet but there are lots more. The downside is that there will be ads on the page and you will probably get a fair bit of email advertising from them.