Add to Chrome.
Click 'Add extension' above.
The installation process should take less than a minute.
Next, you'll Create an Account.
You might also find your answer in the LastPass Enterprise Manual.
What happens if the password the user has to login to Windows is not the same as the password for the pre-existing LastPass account?
The user will see a bubble from LastPass icon in the tray that says "Login failed, does your Windows password match your LastPass password?"