A Distribution Certificate identifies your organization within a distribution provisioning profile and allows you to submit your app to the App Store.
You will need to create only one Distribution Certificate for your Developer Account even if you have multiple apps.
You'll require a Certificate Signing Request (CSR) for creating the iPhone Distribution Certificate.
Click here for a guide on how to create a Certificate Signing Request (CSR).
Follow these steps to create an iPhone Distribution Certificate.
You'll be prompted to add a password to it while saving your certificate file. Keep this field empty and DO NOT set a password for the certificate.
You’ve now successfully created the iPhone Distribution Certificate.