UNIX Create User Account

How do I create a user account under UNIX operating system and assign a password to user account so that he / she can login into server or UNIX workstation?

You need to user the useradd command under UNIX operating systems to create user account and password command to set a password for the same. You need to login as root user to add users. Usually, /etc/passwd, /etc/group and /etc/shadow or /etc/master.passwd files are required for user account management.

Example: Add A User Called Tom Under UNIX

Create / add a user called tom with home directory, enter:
# useradd -m tom

Setup A Password For Tom

Type the following command:
# passwd tom
Make sure password must be 8 character long and include special characters and digits for security.

How Do I Add User Jerry To A Secondary Group Called Sales?

Type the following command:
# useradd -G sales -m jerry
# passwd jerry

How Do I Add /bin/ksh as A Shell While Creating A User Account?

Use the following syntax:

useradd -m -s /bin/ksh username

How Do I Setup HomeDirectory Path While Creating A User Account?

Use the following syntax:

useradd -m -s /bin/ksh -d /path/to/home/user username

You can pass all those options as follows:
# useradd -d /nas/users/v/vivek -m -s /bin/bash -c "Vivek Gite" vivek
# passwd vivek

Further readings:

See useradd and passwd command man page:
man useradd
man passwd