Cinemachine 3.1.1 Unity 6 Virtual Camera

In Cinemachine 3.1.1 Unity 6000.0.19f1 how do I access virtual camera? or its equivalent functionality also after installing the package i keep getting following syntax error:

Library/PackageCache/com.unity.cinemachine/Runtime/Components/CinemachineSplineDollyLookAtTargets.cs(45,36): error CS0246: The type or namespace name ‘IInterpolator<>’ could not be found (are you missing a using directive or an assembly reference?)

We don’t get this problem. Have you tried deleting the Library folder then re-opening the project and re-installing CInemachine?