The debugger file is best deployed as MU plugin so it can load early in the WordPress load order.
Assuming you are in the root directory of WordPress, run the following terminal command:
curl https://raw.githubusercontent.com/andypotanin/wp-debugger/master/wp-debugger.php > wp-content/mu-plugins/wp-debugger.phpSmall utility for debugging WP load times.
Requires https://chrome.google.com/webstore/detail/chrome-logger/noaneddfkdjfnfdakjjmocngnfkfehhd extension for Chrome.