The EC-2V is a two-channel voltage data logger that needs to be plugged in to the mains socket you want to measure.  Setup the Logger using the Electrosoft software, then plug it in.
 
This logger can be installed by anyone when fitted with a plug.  Once you're set up, just turn on the voltage supply/socket to start logging.  The indicator will flash Green when logging.
When the logger's finished recording (or you've captured enough data!) just disconnect from supply, hook it up to your PC and download the information.  Electrosoft will let you view the data immediately on-screen and save or export for later analysis.