You can upload images directly from your PC or device, although you can only select one file at a time.
1) Scroll down to the box for entering text etc. at the bottom of the thread.
2) Click on "Upload a file"
3) Click "Browse" and select the file on your PC or device
4) A thumbnail of your image will appear at bottom left of the reply box.
5) Click on "Thumbnail" or "Full image" (tip: Thumbnail is best, because full images can take sometimes result in the thread taking an eternity to load when a member clicks on it).
6) Click on "Post reply" and that's it, you're done!