You should be able to upload your app through the GUI, I believe under Manage Apps. It will automatically try to vet the app for you and indicate anything that needs to be fixed. Depending on the app, it may still require you to have Splunk Cloud Ops do some vetting, which you can do via opening a ticket.
Check out this here:
I think you need to upload the app file that contains all folders and .conf files and Splunk supports vets it and installs it then.