Download the firmware from the link above, connect your printer to your computer with a USB cable, then use Cura to upload the firmware to your printer.
PID is a method to control the temperature in a more sophisticated way. It might affect very shallow prints; in my experience tall prints (i.e. more than 10mm tall) are unaffected, and really all the bed temperatures does is to keep the plastic stuck to the bed and prevent the bottom layers from warping. Check out my print here
where you can see that there is no way the top of the print was affected by the bed temperature. This was printed in ABS with no enclosure.