The process to create a Certificate Signing Request in a MAC OS computer is very simple.
1. First, go to the Keychain Access utility
2. Go to Keychain Access -> Configuration Assistant -> Request a Certificate from a Certificate Authority ...
3. Enter an email address and name for the Certificate and select "Saved to disk".
Note: CA Email address is not required since you selected the "Saved to disk" option.
4. Click "Continue" and select a location for the CSR file.
Your Certificate Signing Request has been created; you will need this file later when creating the Certificates for the Push Notifications Service.