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.