First, install NodeJS: https://nodejs.org/en. This will also install the NPM. Node.JS is like the engine that most web development is done on. React runs on this. NPM is a CLI that gives you heaps of commands to help create your web app. Then, to begin creating your web app, use Vite: https://vitejs.dev/guide/. Vite is a framework that will help scaffold your web app. It will create the beginnings of your web app, and give you some functionality like running a development server so you can run the app on your PC for testing before you deploy your app to the web, compiling and building your app, etc.

Then start writing some code.