If you already have your SSL Certificate and just need to install it, see
Website Pro SSL Certificate Installation.
How to generate a CSR in WebSite Pro
Open the Website Server Properties and click on the Key Ring tab.
Click on New Key Pair.
Fill in the appropriate fields with your DN information. Do NOT choose a Certification Authority.
Click on Done.
Your CSR is saved in the file you specified, but is also already on the Windows Clipboard. Paste it into the DigiCert form (including the BEGIN and END tags).
After you receive your SSL Certificate from DigiCert, you can install it.