Creating a CSR on Courier IMAP is exactly like creating a CSR for Apache installations. Please follow the Apache CSR instructions here to continue:
Creating a CSR for Apache Linux/Unix
Now navigate to the location of your saved CSR and open it with a suitable text editor such as Notepad, TextEdit, or vi. Copy the entire text - including the top and bottom dashed lines. You can paste this text directly into the VikingCloud Control Center - Submit your CSR to proceed to validation.