The place to start is the instructions that come with the Powerlogger. Until you read those, you're not going to know what questions to ask, and you'll be asking questions that people won't answer because it's in the manual.
It's a simple device and the instructions are well written. You can find them with Teh Googles.
Any sensor sharing is done by splicing the signal wire and running it to the Powerlogger expansion board.