Hello! @LastPass User
Welcome to the LastPass Community.
This should be an automatic process, by the time the LastPass browser extension recognize a new log in that is not saved in your account you should get the pop-up asking to save the password, in case you cannot see it, please try to clean the browser and try again.
Could you please clean your internet browser (cookies and cache), log in to your LastPass account again, and try to replicate the issue?
In case you are still getting the same scenario, please remove the LastPass extension from your internet browser, and in case you have any other extension installed, please try to turn them off. Once that is done, clean your internet browser again, reinstall the LastPass extension, and try again.
Please let me know if you need additional help.
Greetings!
Verlaine | Customer Care