Start Profile Manager
Login to the server, and in the Services list, click Profile Manager.
Make sure to choose the "Settings" option, then click on "Edit" button.
In the Manage Certificates screen, click on the plus sign and choose " Create a Certificate Identity"
Please make sure to tick "SSL Server" in the Certificate Type. Also enter a name for the certificate for reference.
This step would create a self-signed certificate, which is required before you can generate a new CSR.
In the Certificate Information page, leave the value as default.
Next please enter the distinguish name of your CSR.
Select keysize as 2048 bit
Leave the key extension as default
Leave the Basic Constraints value as default
At this stage, you can enter the Subject Alternate Name if you like
You would see a certificate summary page
Click on "Allow" to export the key
Go back to server.app and then Manage certificates
Now click on "Create Certificate Signing Request (CSR) as shown in the diagram below.
You should see a CSR at this stage, you need to use this CSR for enrollment of your SSL certificate on the Thawte website.