In order to log into your computer using command prompt, you need to know the name of your computer and the username of the account you want to log in with. To find the name of your computer, open command prompt and type "hostname". The name of your computer will be displayed next to "HOSTNAME". To log in with a different user account, type "net user [username] [password]", where [username] is the username of the account you want to log in with and [password] is the password for that account.