Since they're film caps, they don't have a polarity. As for the pins, I was similarly confused by a 4 pin WIMA cap recently. But when I tested resistance between the pins, I found that the two pins on each short side are wired together -- i.e., they are electrically the same pin. I suggest measuring the DC resistances yourself to verify. If you get the same results, then you just treat the cap as a regular two terminal film cap and connect +ve to one short side and negative to the other short side. (and, again, which side you chose for +ve or -ve is entirely arbitrary). I chose to externally wire together each pair of short-side pins on the off-chance that each pin connected to a difference spot on the same internal "plate" (doubtful, but it only required me to use an extra 1.5" of wire).
Hope that makes sense.
cheers, Derek