upload direct from your computer searinox, if you click reply to a message there are four tabs at the top of the message box, click 'options' then it opens a box where you can 'add/update' click that and browse to the image on your hard drive, then when it's uploaded click 'save' and you're done. Just make sure your image isn't too big, if you try & keep it to less than 500kb you should be ok
look forward to seeing your work
*edit* ok searinox, it seems like you're managing to upload from your hard drive, but i forgot to say, you can only upload one image per message box, just keep replying to yourself to upload them all, i've just had a quick look and the images seem quite large, don't forget to resize them