Once you have created your VPS you should be able to log in using the connection method specific to that OS/VPS. For example if you installed a VPS with Centos you would connect via ssh to the IP assigned to the VPS on port 22 for SSH. If it were Windows you would connect to the VPS IP via RDP. You can also control the VPS (from the host system) using the command vzctl enter <VPSID>, if you do not know the VPS ID you can find it using vzlist -a.