How to unlock Kindle Fire 8.9


I am trying to install Google Play on my Kindle by following the instructions here…

I’m using Option 2 and the instructions were perfect until I got to the part where it says to “Unlock your Fire tablet and agree to the “Allow USB debugging” request.” Well, I don’t know how to unlock my Fire tablet. I looked online before posting here for any instructions how to do that but I don’t want to accidentally reset my Kindle. So can anyone tell how to unlock the fire tablet, so I can proceed with the instructions, please.