If you are integrated with a CRM then most of the time you click on the relevant E-Marketing button and up pops the platform without a log in screen.
Even when integrated with a CRM you still have a Username and Password for the platform that is stored against your CRM user. These details are used to log you in automatically. If you see the log in screen then this often means that cookies are being blocked which is preventing the auto log in from working. Allowing cookies and trying again will resolve the issue for you.