Tried running a command "sudo apt update" in Ubuntu [closed]

I get my username is not in the sudoers file.I tried various commands to make my username to be in sudoers file.

COMMANDS i tried:sudo visudo, then add ria ALL=(ALL) ALL (getting a msg --> bash: syntax error near unexpected token '('
sudo nano /etc/sudoers.d/ria-grant-root (getting a msg --> username is not in the sudoers file