Dell Power Manager- Power source for laptop

Hello everyone,

I have been using Inspiron 3585. I read a lot of information on Dell Power Manager, but I still don't quite understand. I want to set my laptop to start charging at 80% and stop charging at 100%, afterwards to use the power directly from the AC charger (i.e. power from being plugged in) and not from charging the battery. Can someone tell me how to do that, please.

Thanks.