Navigate to "SSO | SSO Servers", click the context menu of "Single Sign-On Server"

Select "Replace Certificate" from the context menu

In the "Replace Console Certificate" dialogue box either select the pfx file of your current commercial certificate (and CA certificates if required), enter the certificate password, and click on "Save".

Alternatively,  if you already have the certificate under "server certificate" in the Admin Console Repository, then click on "Select Server Certificate" instead.  

Select the correct certificate from the Server Certificate list and click "Save"