Create the forum post and then reply to it. It's easy to attach a photo to a reply (see below)
I just tried out using the "img" tags to embed a URL (internet link rather than a local file).
Put [ img ], then the URL and then the closing tag [ /img ]. Remove the spaces from those tags - I had to put spaces in them to stop them from being interpreted as tags.
Thanks. And thanks for the squirrel pic, made my day so far
If you want to post a picture of your own, just upload it via the "file" link at the bottom, by the Preview and Save buttons, then embed it as above using the img /img (in square brackets) and inserting the file name it shows once you've uploaded your image file.