The microphone is a single mono element. You can select whether you want it to be on the Left or Right channel by connecting the Select pin to power or ground. If you need stereo, pick up two microphones!
You can set them up to be stereo by sharing the Clock, WS and Data lines but having one with Select to ground, and one with Select to high voltage.
This I2S MEMS microphone is bottom ported, so make sure you have the hole in the bottom facing out towards the sounds you want to read. It's a 1.6-3.6V max device only, so not for use with 5V logic (its really unlikely you'd have a 5V-logic device with I2S anyways).
Many beginner microcontroller boards don't have I2S, so make sure its a supported interface before you try to wire it up! This microphone is best used with Cortex M-series chips like the Arduino Zero, Feather M0, or single-board computers like the Raspberry Pi.