First of all, if youre just starting out why do you want to break the bank with PWs ?? There are great triggers available that do exactly the same thing for much less $$$.
I use the Cactus V4s. You connect the flash to the receiver via a hotshoe, and the receiver has a screw thread in the base that will allow you to mount the receiver onto the softbox mounting bracket.
Yongnuo also make a similar product to the Cactus, and are even cheaper again.
There are also plenty of pop-up speedlight softboxes available as well.
Check this out
Mate you can honestly set this up for under $150 total (excluding the flash of course). The softbox is about $60, and You can buy a Cactus Trigger/Receiver Set from
here for $65.
Two PWs will cost you about 500 bucks on their own.