If you click add an attachment the page reloads and under the blue banner that say "add an attachment" Click browse, selct the file you want to upload, click OK, then click add attachment.
Just to prove that it works like this I will attach a file.
lol, may I congratulate you on posting the image twice (are you trying to make a point...?) :lol:
as goodpickles says, after clicking add an attachment, the page will reload. CLick browse, select the file you want to add, then click 'add attachment' (but the other one to the one you first pressed). The page will reload, and it will look as if you have uploaded nothing, but you will have.
Also, you can only post certain file types and sizes