Just click on the button ''Go Advanced'' then underneath the box where you type there is another button saying ''Pictures upload''. Click on that too. Then a new window box pops up and you must click on the right side the button saying ''Add Files''. A new smaller window appears and you must click the button saying ''select files''. After you click on that a large window in your windows explorer will pop up and you can search the file that you have your photos saved (in your hardisk).
You click on the images and then click on ''open'' which is in the right lower corner of the window.
In the small gray window that opened before you will see the filenames of the photos you have chosen. Underneath the is an option saying ''upload files''. Click on that and the photos will be uploaded. When it's finished close that greay small window and click on ''submit reply''.