Do not use the Back button on your browser when using CPQ.
Before you log in to CPQ, make sure you meet the following criteria.
You have installed all of the required CPQ module packages.
You have administrative privileges.
You have login credentials provided by Apttus.
To log in to CPQ
Go to http://www.salesforce.com/. Or If your organization is using a sandbox or test environment to access Apttus CPQ (for example, if you are doing user acceptance testing), go to http://test.salesforce.com/ instead.
From the toolbar at the top of the page, click Login. The login page opens.
Enter your user name and password, and click Log in.
Navigate to Apttus Proposal Management to access the proposals.
In Salesforce Classic: Click the App Menu
In Salesforce Lightning Experience: Click the App Launcher.