It is best not to use root user for anything as root is a common user name. It’s better to create sudo users for these purposes.
Here’s the easiest way to add a user to sudo group.
First create the user you want:
sudo adduser somik
Adding user 'somik' ...
Adding new group 'somik' (1000) ...
Adding new user 'somik' (1000) with group 'somik' ...
Creating home directory '/home/somik' ...
Copying files from '/etc/skel' ...
New password:
**PASSWORD**
Retype new password:
**PASSWORD**
passwd: password updated successfully
Changing the user information for somik
Enter the new value, or press ENTER for the default
Full Name []:
**NAME**
Room Number []:
Work Phone []:
Home Phone []:
Other []:
Is the information correct? [Y/n] **Y**
Then add the user to sudo group:
sudo usermod -aG sudo somik
That’s it. Now login as the user.