Well, even if you did manage to give them the right signing keys (Provisioning Profile and ".p12" Certificate) you wouldn't be able to export this way. In order to use Cocoonjs you have to do the signing part yourself. This won't be a problem as long as you've got a Mac. When exporting to iOS through cocoon without signing keys, they will send you a direct download link giving you a ".xarchive" file. You will have to sign this file in order for it to become a ".ipa" file. To do so, open it with Xcode. (You should have both the Provisioning Profile and the .p12 certificate created and installed in your computer before openning it) Now you should see a window in which you can tell Xcode where and how to you want it to be exported. After you choose it will automatically search for Profiles, certificates and Bundle IDs that can be used to sign the file.
If you don't have the ".p12" yet, here's a link that will help you get it.