hi Sarah
At the bottom of the mobile site is a link to 'full site'. I'm not sure, but this may make you able to do the upload.
Also, we have a section of the forums for questions like this, it's called User2User Tech. Misc is an active section and tech/site questions may get lost in the shuffle, but the User2User is much slower and aimed at such things, so it may be a better option in the future.