Hi hyju,
It's a bit complicated.
You would have to download the file from here, open it, insert the upgrade cover using the same name format so it appears at the Front of the files (jpgs only please), and then upload the entire file again adding
'-Upgrade' at the end of the file name but before .cbz, .zip or whatever the file format is. We ask that none of the other original pages be adjusted in anyway and the original scanner be given full credit in the description area.
Sadly, we can not add a single jpg into a file from our end on the server.
For a tutorial on how to upload a cbz, zip, etc file onto the site you can read the tutorial here -
http://digitalcomicmuseum.com/forum/index.php/topic,1882.0.htmlThanks for asking,
-Yoc