Not able to configure wireless connection

Issue

• Cannot configure wireless connection due to the following :

• When "sudo system-config-network" is executed, prompt for 'root' password comes up. On entering it a message comes up saying :

<username> is not in the sudoers file. This incident will be reported.

• When trying to add in the list of privileged users, using command below command:

# usermod -G <username>, wheel <username>

• The following message appears :

bash: usermod: Permission denied