Try the Variant Manager User's Manual delivered with the product.
will it be in installed folder under help
You need to explicitly install the help files and they get installed to the docs folder. Once installed you can quickly jump to the Variant Manager User's Guide by pressing F1 whilst in the VM window.
Two things that may help to get your required output.
1. Within Variant Manager there is a Generate PCB Variant View, which will remove/change components on your design based on the variant settings.
2. (Provided you have a Fablink Licence available) then from the output menu within xExpedition you can output a Bill of Materials and you can select which variant (or all variants) to include in this report.