How do you change heater core in 91 cavalier?

To change the heater core in a 1991 Chevrolet Cavalier, first, disconnect the negative battery cable and drain the coolant. Remove the dashboard and the heater core cover to access the heater core. Disconnect the inlet and outlet hoses, then unbolt the heater core from its housing and replace it with the new unit. Reassemble the dashboard, reconnect the hoses, refill the coolant, and reconnect the battery.