If you have registered at Lecturio via Facebook, you can also log in with your e-mail address.
Just use the e-mail address you use on Facebook. To generate a password, you can use the function "Forgot your password".
Deleting your Facebook account does not affect your account at Lecturio. Your Lecturio account is still available with the e-mail address you used on Facebook. Just generate a new password using the function “Forgot your password” and log in with this new password.