Go to /etc/ips
and remove the line with the IP you want to remove.
Other way to add multiple IPs on a non cpanel is
Go to /etc/sysconfig/network-scripts/
Then add ifcfg-eth0:1 with different ip.
For example
DEVICE=eth0:1
ONBOOT=yes
BOOTPROTO=static
IPADDR=172.18.0.15
NETMASK=255.255.0.0
