To run the samples follow these steps:

Make sure Node.JS LTS is installed and execute the following commands in the sample directory:

npm install

Open the Chrome Extension Management page by navigating to chrome://extensions.
Enable Developer Mode by clicking the toggle switch next to Developer mode.
Click the LOAD UNPACKED button and select the quickstart directory.
After the extension is added, it will get an extension id displayed that will be visible in the Extension Management page.
Set the Callback URL in the Application Settings to

https://<YOUR_EXTENSION_ID>.chromiumapp.org/auth0

chrome-extension://<YOUR_EXTENSION_ID>

The extension can be executed by clicking the icon with an [A] in the Chrome toolbar.

What technology are you using for your web app?