You can find your servername in the Welcome Email or by contacting support.
The preferred URLs for SSL access are:
https://servername.solardns.com:2083 for cPanel
https://servername.solardns.com:2087 for WHM
https://servername.solardns.com:2096 for Webmail
e.g. https://mercury.solardns.com:2083
You can also just access via https://yourdomain.com:2083 for example for cPanel but you will receive an SSL warning because the certificate won’t match your domain name. In some browsers you can permanently accept the certificate so the warning won’t come up in future.