When posting, just click the "Insert Image" toolbar button, which looks somewhat like a picture of a tree in a frame. On the "Quick Reply" toolbar, this tool is the third button from the right. After clicking the button, you'll get an "Insert Image" dialog box, on which there are two tabs - one to upload and insert an image from your computer (or your iPad "Camera Roll"), and one to insert a link to an image on a web server by entering a URL.
Just try it in a response to this thread. It's pretty easy. Good luck!