Yes, you would connect the external 24VDC supply per page 4-14 of the manual depending on if you are sinking or sourcing the inputs. Is there a reason where you need an external power supply? There are a few things to be followed, one is the diode when sinking, and the other is any noise or voltage spikes if the external power supply is used to power anything else. If the same power supply is used to power relays or contactors, when the coil is released it can put a reverse voltage spike of around 150V and burn out other components if you do not use reverse diodes across the coils. Other issues can be be electrical noise giving false signaling. In most cases I use the WJ200 internal power supply which is 24VDC @100mA and power separate relays/contactors via a separate 24V power supply.