The HPWC is an external charger that gets installed by an electrician close to your panel in the garage. Since you have dual chargers onboard, the HPWC can be set to deliver up 72A (80% of a 90A breaker) of current, which will give you 52miles of charge/hour.
Problem is... the previous owner of your car did not remove the HPWC and include it as part of the sale. If they did, you’d be wondering what that silver alien-head-like thing in the trunk/frunk was.
So, you need to either buy a new HPWC or at least have an electrician install a NEMA 14-50 outlet in order to charge at more than 4mi/hr.