You can do this in 2 methods- however, IMHO method-2 usually works great for me.
Step 1: Verify the Wheel Group is Enabled
Your CentOS 7 installation may or may not have the wheel group enabled. Open the configuration file by entering the command:
Scroll through the configuration file until you see the following entry:
## Allows people in group wheel to run all commands # %wheel ALL=(ALL) ALL
If the second line begins with the # sign, it has been disabled and marked as a comment. Just delete the # sign at the beginning of the second line so it looks like the following:
%wheel ALL=(ALL) ALL
Then save the file and exit the editor.