You could send the picture to your email, save the picture on your computer, and get ready to post it on the thread. Once you do this, choose "More Reply Options". If you scroll down you will see a text that reads "Attach Files" where you would click on "Choose File". Once you choose your file, you will need to click "Attach This File" and then the picture will come up. After this you would click the "Add To Post" text and you should be ready to go! Good luck!