AT the bottom of the ‘post a reply’ page (where you type in your message), there is tab ‘upload attachment’). Clicj on the tab, click on ‘browse’ to select your photo from your computer, once selected, click on ‘add the file’ in the upload attachment tab. You can insert a caption (‘comment’) in the box beneath the filename box. I limit my photo file size to around 200kb (use image processing/re-sizing software if your photo files are too large).
Hope this helps,