This board does not support file uploads. Please use an external service to upload the image there and then reference it here. An example for an external service is ImageShack: http://imageshack.us/
When you have uploaded the image, ImageShack will provide you an link to post into an forum. If they provide an BBCode-Link, then you just have to copy it here, otherwise paste the normal http-Link here, mark it and press the Img-Button.