on each sub, wire the voice coils as such, wire positive of one coil to negative of other coil( called series), do the same to other sub.
now you should have a positive and a negative left over on each sub, connect these wires to their corresponding spots on your terminal cups, if your just using a box with a hole in the back with wires coming out then skip this step.
now were wiring the subs parallel. So connect both positives together, and both negatives together and connect wires to amp, now you have a 2 ohm load.
next time you need help with sub woofer wiring issues and impedance, use this calculator, it pretty straight forward, and show you decent diagrams with all options for final impedance.
Subwoofer Wiring Diagrams