Mac users have a few options for generating a certificate signing request (CSR) for a personal authentication certificate. The easiest method is to create your CSR in Keychain. 

To start, open the Keychain Access Menu.

Click Certificate Assistant, then click Request a Certificate from a Certificate Authority.

In the Certificate Assistant window you will enter the certificate user email address as both the Common Name and the email address.

You do not need to enter the CA Email address.

For Request is, select Saved to disk. Then click Continue.

You can set the file name with the extension .certSigningRequest and select a location to save it.

Once you click Save, you can locate the CSR in Finder.

You will need to open the CSR in TextEdit to view the code. 

Copy all of the text, including -----BEGIN CERTIFICATE REQUEST----- and -----END CERTIFICATE REQUEST----- to paste into your personal authentication certificate order form.

On the order form, select Manually Enter My CSR and paste the text in the field.

Once you have completed the order form, you will receive your order ID number and move on to the validation step.