Click the Sign in as a different User link to sign in as a different user. Once you perform this step, all the cloud data associated with this data file will be removed. You will no longer be able to get latest credit score / get the latest online bill / use Life Yield Tax Optimizer using the old Quicken ID, once you perform this step. You will have to re-register for credit score, online bills, Life Yield Tax optimizer and also re-sync all the data to cloud on the new user ID that you are signing in with (These features are not available in Canda).
If you would rather delete all your data on the Quicken cloud and start over, delete your cloud data instead.