In UNIX you can added users in two ways. You can do it manually
by editing the right files or you can use the built in script (adduser)
that asks the right questions and does the addition in the background.
If you want to do it by hand (which is a good thing to know) here is a step by step process to add a user. (I don't want to repeat myself so use the same process to delete a user)
In Windows NT select Programs --> Administrative Tools --> User Manager. User --> New User. Fill in the fields for username, fullname, description, and assign a password. Don't forget to confirm the new password. It is probably a good idea to check "User must change password at next logon" because assigning passwords to people can get hairy for the administrator and could be a security hole if you have to write them all down. The next step is to assign a user to the right groups.
Select the "Groups" button at the bottom of the New User box.Simply select the groups that you want the new user to be in and click the add button. Click OK to return to the New User box.
The "Profile" button allows you to set a local home directory , a user profile path, and a logon script name for things you want to run when this user logs on. Note it is a good idea to create a /user or /home directory for holding the user's home directories.
Next, you may want to assign certain hours of operation for the new user. Click the "Hours" button at the bottom of the New Users box. In here just select the hours of operation by using the mouse and selected the hours. Not very difficult :) When you are done select OK.
In some cases you may only want a user to be able to log onto certain machines. Click the "Logon To" button and fill in the names of the acceptable computers then click OK.
Finally, click the "Accounts" button from the New User box, in here you will be able to set the expiration of the account and the account type.
Don't forget to test the account.