VERY IMPORTANT: In the email you received from VikingCloud when your certificate was issued, there is a ZIP file. Within that ZIP file is a file that ends in .p7b. This is the only file you will need for the installation. The .p7b is the only file necessary for installation on Microsoft IIS/OWA servers. Transfer the .p7b file to the Windows Server.
Open Internet Services Manager from the Administrative Tools. Right click on the OWA website where you previously created a CSR and choose "Properties". Press the "Directory Security" tab and then click "Server Certificate" in the "Secure Communications" section.
When the wizard starts, choose "Process the pending request..." and press "Next". In the next screen, click "Browse" and then click the drop down box to choose "All Files *.*". Now, navigate to the folder where you stored the .p7b file and select it. Press "OK" and then click next. Verify that the port number is correct (customers who are renewing a certificate will not see this step). The default SSL/TLS port is 443. Finish the wizard and your certificate and intermediates will be installed.
Your new certificates are available instantly - there is no need to restart IIS/OWA or the server itself. However, if you have a Microsoft ISA 2000/2004 server in front of your IIS/OWA server, you will need to follow the installation instructions for the Microsoft ISA Server as well.