Connect the PeTrack to the AC adapter via the USB cable that came with the unit. Allow it to charge overnight or more than 4 hours at the very least. When you're done charging the unit and have disconnected it from the wall adapter, make sure to power cycle the unit. Just turn off the unit and turn it back on, to make sure you know in what state the unit is in.
To know if your device is powering on or off, refer to How would I know if my PeTrack is turned on or off?