- Go to developer.apple.com -> Account -> Certificates
- Select Certificates->Production-> Add
- Choose App Store and Ad Hoc
- Open Keychain Access app and select Keychain Access > Certificate Assistant > Request a Certificate from a Certificate Authority as stated in the developer website
- Fill out all values and don't forget to select "let me specify key pair information" this will ensure that a private key is specified in your generated cert
- Save the cert request
- Select continue and choose the saved cert request
- This will generate you new distribution cert
- Go to provisioning profile and select the one you're using to provision your app
- Change the used distribution cert to the one you newly generated
- Go back to xcode and refresh your certs within prefs->account
- Download the newly generated provisioning profile if not already done
On any other machine you need to get access to the distribution profile including the private key to sign ios application. You need to export the distribution profile from the machine, which generates the profile as a p12 file. Just choose export within the key list and provide a password.
On the second machine you could then open the p12 file provide the password and that imports the dist cert including the private key into your local key store.