Adding breakouts for external components in Eagle PCB
You could use an appropriate connector footprint - you don't need to install the connector.

Or you could make a suitable footprint yourself - it probably just needs a few pads with holes of a convenient size to solder the wires.  You would also want an appropriate schematic component to go with the footprint.

If you do any amount of PCB design, you will have to make your own PCB footprints and schematic components.