We'll be making it a lot easier tomorrow to add images to your blog posts tomorrow. Just select the "Add Attachments" link (to the right) and upload your image. Automatically, a link that looks like this will be added to your blog post:
[[image=MyRecordings.png]]
Keep it where it is or move it to where the image is and that's where the image will show up. If you use image=http://..., that particular image will be included on the page. Otherwise, it will assume the image is an uploaded attachment and try to use that.