In Excel, only the root certificate is necessary to get access to the server. Make a copy of the root certificate and name it client.pem. Then move client.pem to <Install_path>\xladdin\cert\
When creating a connection, use the correct server address that matches the CN used in the server certificate.
The port is the HTTP Port.
When connecting, the server redirects the client to https. The client will use the client.pem root certificate in <Install_path>\xladdin\cert\ to establish the connection.