If you need to add a new user to your systemm just run the following commands:
useradd username
That will create a new user, and a new group, for the ‘username’ that you placed in there. Now, to change the password for that user, run this:
passwd username
The system will ask you to input the password for the ‘username’ you chose twice. Thats it, make sure you read the article on ssh security on how to make your enviroment more secure.