In CBT, Screenshot testing - How to verify for Login and compose page in gmail ?

In screenshot testing, I load a page in the URL bar and see the screenshots for different environment configurations.

Step 1: I'm validating the login page of the application

Step 2: I've to validate the compose page after login in. 

Question: How to login by giving user credientials and navigate to compose page in screenshot testing ?

because i cannot copy paste the URL of compose page link as this is a live session in my application.

Regards

Valla