Use "gpasswd -a" to add users to the group. Execute with root privileges with sudo.
sudo gpasswd -a username group name
This is a sample to add kimoto to myapp-group group.
sudo gpasswd -a kimoto myapp-group
Users added to the group can be found in the /etc/group file.
sudo cat / etc / group
This is an output example.
myapp-group: x: 1009: kimoto, ken