Would love to help but your photo link didn't work correctly. If you are uploading from your pc, and it looks like you are, you need to do it a different way. Look below the message box you type in. Is there a button that says "go advanced?" If there is not, or after you click it, scroll down and there is a button that says "manage attachments" You want to click on that and you should get a pop up box. Click "choose file" and select the file on your pc, and the click upload, then click "close box" this should upload your photo.
The link you used is for a photo already on the internet on a service such as Photobucket, flickr etc.
When I first came on Horse Forum it was really confusing to me. I hope I have helped.... can't wait to see what kind of martingale it is :)