There are several steps involved in connecting a NodeMCU to a web app:

1. First, you will need to set up your NodeMCU with the necessary software and libraries. This typically involves installing the Arduino IDE and installing the ESP8266 library.

2. Next, you will need to write the code for your NodeMCU that will handle communication with the web application. This might involve setting up a web server on the NodeMCU or using a library such as ESPAsyncWebServer to handle incoming HTTP requests.

3. Once your NodeMCU is set up and configured, you can connect it to your web application by using a protocol such as HTTP or WebSockets. This might involve sending data from the NodeMCY to the web application, or receiving data from the web application and using it to control the NodeMCU's outputs.

4. Finally, you will need to test and debug your NodeMCU-web application connection to ensure that it is working properly. You can use tools such as the Arduino IDE's serial monitor or the Chrome DevTools to debug any issues that you encounter.

It's worth noting that connecting NodeMCU to a web application is a broad topic, and the exact steps may vary depending on the specific requirements of your project and the resources you have available.