Error message as not a sudoers

[sadhanabhattarai]

After installing the docker, I tried this in putty and it gives message as sbhatt21 is not in the sudoers file. This incident will be reported.
$sudo apt-get install docker.io python3 python3-pip python-pip zlib1g-dev libxml2-dev
$sudo usermod -aG docker sbhatt21

[jorvis]

On which server did you try to run these commands? Or is this on your own machine?