Soren, clicking on the "insert image" icon or uploading an attachment is completely different from just using a link to an external website or using the img tag.
Firstly, you need to have the image hosted (use imgur, tinypic, whatever). Then copy/paste the url (www.com/imagecode.png/jpg) and simply type [img] before the url and [/img] after it. Or don't even do that, a link is always more welcomed than an attachment.
Example: image's link is www.images.com/image1.png, then the code becomes [img]www.images.com/image1.png[/img]. And that's it.
Aside from that, the image is absolutely terrible from almost every standpoint, you -REALLY- need... to watch tutorials.