Often because you are logged into LInkedIn so often it is hard to remmeber the password which is needed to Integrated with Launched so that Nova can connect, send messages on your behalf.
There are great tools out there like https://www.lastpass.com/ which stores all your online password.
If you do find you cannot remember your LinkedIn details, however you are logged in, then it's really easy, just go to https://www.linkedin.com/mypreferences/d/change-password
and click Show
Your email account will be visible