1) have a root privilege shell or be on the sudo list.
2a) At a root shell prompt (#)
yum install net-tools
2b) User account on the sudo list
sudo yum install net-tools
If the package is installed it will state so and exit yum. (Then it sounds like a path issue). If not installed yum will prompt the user to continue after a few local / network package checks. The install will (should) take but a moment.. presto ifconfig is now installed.
If you feel adventurous.. The equivalent of using ifconfig in displaying the interface / address information using ip
ip addr