Log in as an administrator level user account.

Access the user management options in the Administration block under Site administration | Users | Accounts.

Click on Add a new user. This brings up the following page:

To fill in the Username, use the person's first name and last name with no spaces and all in lowercase for the username.

The username column must be all lowercase using letters, numbers, and any of the following characters: hyphen "-", underscore "_", period ".", or an at character "@".

If you are creating an account for a user with external authentication, then select the relevant option for the Authentication method, otherwise leave the Authentication method to Manual Accounts.

Create a secure password for the user and enter it into the New password...