If you already have your SSL Certificate and just need to install it, see SurgeMail SSL Certificate Installation.
How to generate a CSR in SurgeMail
In the Web Admin, go to the Globals page.
Click 'SSL Certificates Configure'
Click the 'New CSR' button. This will start the process of generating a new CSR, a new private key, and a temporary certificate (unsigned).
When prompted, fill out the company details for the company for which the certificate will be issued.
Copy the new CSR and paste it into the DigiCert order form.
After you receive your SSL Certificate from DigiCert, you can install it.