After loggin in the VPS Control panel you can chose any of your server and perform basic management functions:
Rebooting your system in case your system has crashed and inaccessible. Manage -> General -> Reboot
Reinstalling your system in case you need a clean start. We support all current and stable templates listed on http://wiki.openvz.org/Download/template/precreated . If the template you want is missing please open a ticket to let us know and we will add it for you. Manage -> General -> Reinstall
Use the change hostname option. Manage -> Hosname -> Change
You can also change the root password here in case you have forgoten it. Manage -> Root Password -> Change
The rest of the Control panel options are explained in detail in their respective articles.