In order to setup SSL on the customer portal, we will need a pfx file to install. You will need to generate a Certificate Signing Request (CSR) to move forward with this process so we have outlined one common way to do this on a windows machine.
In Windows, type IIS into the search area and select Internet Information Services (IIS) Manager
In the Connections panel on the left, click the server name for which you want to generate the CSR. In the middle panel, double-click Server Certificates.
In the actions panel on the right, click Create Certificate Request.
Enter the following Distinguished Name Properties, and then click Next.
For Cryptographic service provider, select Microsoft RSA SChannel Cryptographic Provider. For Bit length, select 2048 or higher and then click Next.
Click ..., enter the location and file name for your CSR, and then click Finish.