In your Grid service, the SSH is disabled by default, but you can enable it using the below steps.
1. Login to your Account and click on Primary domain.
2. Go to Server Administrator.
3. Change the option to Enabled from Disabled.
4. Click on save to complete.
You can connect to your server by supplying your login credentials like this,
" ssh email@example.com (or) ssh firstname.lastname@example.org "
If you are connecting to the server for the first time, it will show an error and will ask to accept the connection by typing "yes". Type yes and click enter.
Then Provide your password details in the next field like
" Password: "
That is all, now you have successfully connected to your server.