Update applications.mdx

Author: dexhorthy

docs/quickstart/applications.mdx

@@ -26,3 +26,10 @@ npx create-ag-ui-app@latest
   src="https://copilotkit-public-assets.s3.us-east-1.amazonaws.com/docs/ag-ui/quickstart.gif"
 />
 
+Once the setup is done, start the server with
+
+```sh
+npm run dev
+```
+
+For the copilotkit example you can head to http://localhost:3000/copilotkit to see the app in action.