ProbeGirlie, I've had some problems with files that are too large - either by physical size (number of pixels) or by actual size (number of bytes). In the case of the 'physical' size - the server has informed me as I've attempted to submit the post.....
Assuming that your pic exceeds neither of these conditions, you should be able to use the 'attach' function at the very bottom of the page. You can just 'browse' to the file on your hard drive and it will upload it during the submission process.
If your file is too big, then you could do what I have had to on other occasions, and that is to upload your picture to a webspace - either your own if you have one - or a third party site. I use www.geekazoids.net
I have attached a picture for you - for two reasons. Firstly as a demonstration, and secondly so I can show you MY Probe!
I hope that this helps.