At first, you need to back up, if anything will be done wrong. Below you could find command:

Also please make sure that you are one of the root account on your server.
For adding IP address to server’s network interface you need to edit files /root/etc/network/interfaces

After coping, you could view and edit file using nano:

And when you will be there, you should see something like below:

Next one, if you want to add IP below the eth0 and name it eth0:1. It should look something like this:

Because this new IP is going to be set on the same Ethernet port, you will want to set this as eth0:1 and not eth1. All you will need to add is the new address and its netmask. Once you have this set, save and restart your server either within your cloud control panel or with this command:

After rebooting the server, you will have an additional IP on your server.