Only users with full admin privileges can create new users. Users with Admin privileges has full access and permissions to perform all sorts of task on the site. So the role is given only to someone you fully trust.

1. Go to Admin > People > Add a new user
2. Type in the email address of the user you are creating
3. Assign a username
4. Assign password
5. The username and password are usually temporary and can later be changed by the actual user
6. You may choose to notify the person by email that a website user account has been created for him/her
7. Make sure the status is set to active, unless you intend it to be otherwise
8. Select the role you are giving to your user
9. Select the timezone
10. You may leave the rest of the fields to their default setting
11. Click save