If you right click the mouse on a photo, you should be given options such as copy, paste, etc... One of them (at the bottom) should be Properties. Left click on Properties. Then highlight and copy the URL for the photo.
Then, on the posting box here on the forum, you'll see a little box with a picture of the Mona Lisa next to the Flash F in the upper left. Click on the Mona Lisa and it show two sets of brackets with img between them. Between the two inner brackets, paste the photo's URL. That should allow you to post the photo.