Sure you just save the picture to your desktop or wherever is convenient on the computer. Then below the reply window it will say "Go Advanced". Click that and then scroll down to "Manage Attachments". Click that and then a window will pop up that allows you to add the picture file that you want. Once you click on the file you want you will see it in the menu, after that make sure to click "upload" once it is uploaded you can finish the post and the picture will post with it.