See Using IIS 8 to Install the SSL Certificate.
If you used IIS 8 to generate your CSR, you need to use IIS 8 to install the SSL Certificate, The SharePoint SSL Certificate installation process consists of three steps: If you have not yet created a Certificate Signing Request (CSR) and ordered your certificate, see Microsoft SharePoint 2013: SSL Certificate CSR Creation Instructions. Because SharePoint 2013 is designed to run on Microsoft IIS 8, you can use IIS. Microsoft SharePoint 2013 does not include a GUI for installing the SSL Certificate. SharePoint 2013: Installing Your SSL Certificate
