Hi Sirisha ,
You need to do the following (tested in v12.1.0)
From Manage, click on People then Accounts.
Click on the Cognos namespace.
From a role (this is not working with a group) that you will use to apply this modification, click on Actions menu then choose Properties.
Click on the Customization tab then Edit for Home Page:

Select a report or a dashboard..
Click Select to save this update.
Click Save again.
To test, ask one user belonging to the role you've modified to logoff and logon, and it should be working.
Best regards,
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Patrick Neveu
BSL Consulting
IBM Champion
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