You can also add the image as an attachment, preview the post and click on the thumbnail. Grab the URL from the address bar in your browser, and paste that between the [ IMG ] tags as previously stated.
To attach the image, when you're in the advanced editor, scroll down and click "manage attachments" From there click browse to find your pic, then hit upload. Once you do that, click "preview post," click on the thumbnail and it will open the image in a new window. Copy the address from the address bar in your browser, then click the mountain with sun icon (insert image) and paste in the address you just copied.