How do I fill the Optimal Dispense liquid detergent cartridge?

Pull back on the tab and lift the fill door on the cartridge. Fill to the 'MAX' line with HE liquid detergent and close the fill door until it clicks into place. Each cartridge holds about 18.5 oz. (550 ml) of HE liquid detergent, which is enough for up to 36 loads depending on cycle and detergent concentration.