The easiest and most permanent way (not subject to any outside source's rules) is straight from your computer, which is of course free. Instead of 'post quick reply' select 'advanced' and scroll down on the resulting display until you see a 'manage attachments' blank. That will give you the option to select an image from your own computer. 'Browse'. There will be an 'upload' option. A code will appear down near that 'manage attachments'---click on it. That will actually upload the file as a thumbnail, and you are ready to post your comment. Once you post, the thumbnail moves up into your comment box. If a user clicks on your thumbnail, it will expand into a larger image. The result looks like this: