Upload Theme .zip

I have downloaded the psd files to edit the header and some other information, but when I go to upload the new contents I get this error: “In your zip there should be one folder only, with the content of your theme within.” The thing is that there are no other folders only the psd file that I edited.

Any assistance would be greatly appreciated, thank you! : )

http://wordpress.org/extend/plugins/wysija-newsletters/