first take a single sub. Wire the voice coils in parallel. this means, a wire goes from + to + and a wire goes from - to -. two wires.
do the same for the other sub.
Now wire the two subs in parallel but with one in reverse phase.
4 more wires are added.
- one goes from the first sub + to the second sub -
- one goes from first sub - to second sub +
last two connect to first sub + and - and then to amp + and - respectively.
so it should look like this: