Login to Online.net panel, Visit Server>Server list>Manage
Click the Install button.
Choose the type of Distro required. I chose Proxmox.
Select the hard disk configuration.
Validate the install, choose your passwords
Once installed, you need to upgrade proxmox from 2.3 to 3.

wget http://download.proxmox.com/debian/dists/wheezy/pve-upgrade-2.3-to-3.0
chmod +x pve-upgrade-2.3-to-3.0
./pve-upgrade-2.3-to-3.0 --download-only
./pve-upgrade-2.3-to-3.0

If OpenVZ doesn’t work anymore and you installed PVE on top of Debian, you should find out which Kernel is running:

uname -a

To remove the Debian Kernel and activate the Proxmox Kernel, do the following:

apt-get purge linux-base

Update Grub:

update-grub

Reboot.
Now connect to https://yourip:8006

To set up containers in routed mode, you need to order Failover IPs. If these IPs are in a different subnet, you need to edit /etc/vz/vz.conf, and change the

NEIGHBOUR_DEVS=detect 

to

NEIGHBOUR_DEVS=all

Openvz templates for creating containers should be downloaded to:

/var/lib/vz/template/cache/

Ref:
https://openvz.org/User_Guide/Operations_on_Containers#Starting.2C_Stopping.2C_Restarting.2C_and_Querying_Status_of_Container