There is no actual "sender" for a boost gauge. It seems that some gauges (Auto Meter for example) don't come with the proper fitting for the intake. They come with a "T" fitting for tapping into a vacuum/air line. If your gauge didn't come with the proper thread in compression type fitting, you'll have to go get the pieces from your local auto parts/hardware store.
As gmctd said, there are pics in the FAQs of where to tap, you can also go to the Kennedy Diesel site, there are some pics there.
Dave