shells/browser/shared/deploy.chrome.html

<ol>
  <li><a href="RelayDevTools.zip">download extension</a></li>
  <li>Double-click to extract</li>
  <li>Navigate to <code>chrome://extensions/</code></li>
  <li>Enable "Developer mode"</li>
  <li>Click "LOAD UNPACKED"</li>
  <li>Select extracted extension folder (<code>RelayDevTools</code>)</li>
</ol>