Once you have run a password audit and discovered weak passwords you are likely going to want to remediate them. You can right click on an acount in the main window and if there are available remediations they will be displayed. Remediations are available if you imported the passwords from the local machine or a remote machine. They are not available if you imported from a file because L0phtCrack doesn't have the credentials and the associated machine to connect to in order to perfrom the remediation.
To remediate, right click on the account you want to remediate and select Disable Account or Force Password Change from the Available Remediations pop up menu. Multiple accounts can be selected by holding down the shift or control keys while clicking. It is convenient to sort all the cracked passwords, select them, and choose a remediation option. Please be careful not to disable the Administrator account! If you do, you won't be able to get back into it to enable it again.
Due to the sensitive nature of remediation, it may only be performed interactively, and not scheduled.