Not sure without being a paid member if you can access Dirty Bin.
But under this text box where you write your message is a link that say's, 'Attachments and other options'. make sure that you edit out your id code in the lower left corner of the picture, then click this link. It will give you an option to choose a file. Pick the file that you want to upload, double click it and then click post when your done.
Just be sure there are no identifying codes in the pix, IE; the dots, the time, the id code as I mentioned before.