Now take the chin electrodes and stick them on the prepared sites on your chin. The plugs insert into the three remaining ports on the bottom of the headbox (the one from the middle of your chin goes in the middle port, the other two are interchangeable).

For whatever reason, the skin around one's chin is notoriously difficult to get dot electrodes to stick to. But don't despair, just do your best and maybe use some extra tape if necessary.