Even though the "Site load balancing" is not a real load balancer, the Server and clients are "smart" enough to detect when a ThinScale Server is down and can simply connect to another one automatically.
To enable this functionality, you need to have two ThinScale "Primary Servers" communicating with each other and up and running.
The next step is to create a site.
Right-click the Sites tab and select "New Site"
Give it a name, a description, a username and password and check the option "Enable site load balancing".
Add both Primary Server to the newly created site and click Add.
During installation of a new client you can choose which server you want to connect the clients too, but if one of them are down, the client will pick the next available without interruption, giving you time to troubleshoot the one that failed.
if a site was already created, simply add the second primary server to the site and you are done.