username not in sudoers file and access denied to sudoers file

I am trying to install RVM to install ruby on rails in lynux but I get the following message: your username is not in the sudoers file, then when I try to use visudo to edit the sudoers file, the following message appears: access deny to sudoers file. so, can I edit the sudoers file?.

regards

​login as root (sudo su) and then edit the file to add your user.​