The IOS export says I need one.
I’ll be adding some instructions for the iOS exporter, but that’s part of the Apple App build process. You have to be signed up in the Apple developer program ($99 here https://developer.apple.com/programs/). There is a brief explanation of the overall process here: http://escoz.com/blog/demystifying-ios-certificates-and-provisioning-files/
@Thanks
@grazer- can you make it to where we can download the app regardless of the signature? But we can’t post to the store without it?
Take that one up with Apple 
Unfortunately an iOS device will not allow an app to install unless it is code signed, and contains a valid provisioning profile.