@David288
It's surprising you ask this question given you have over 500 Reviews.
There are a couple of ways.
Firstly, when you receive email notification that you can read guest's review, there's a big red box below
Write a Response
Secondly, on the Dashboard, first on the left is HOME:
Scroll down to Notifications:
You'll see recent guests who left a review.
Click on the Guest you wish to respond to (or any recent guest showing)
Profile-Reviews: 'Reviews About You' & 'Reviews by You'.
'Leave Public Response'