Sorry I didn't see this before... So when you are at your Flickr photo's page - right above the picture is a button that says "all sizes". When you click on that it will automatically take you to the picture's large size. You'll see the different options (square, thumbnail, small, medium, large and original) at the top. Click on the size you want to post. When that size comes up, scroll down and you'll see option number 2 - grab the photo's url. Copy and paste it here and there you have it!