Here are the steps to create a React web part:
1. Scaffold a new React web part project:
```
yo @microsoft/sharepoint
```
2. When prompted, select the following:
- Use the current folder for where to place the files
- WebPart as the client-side component type
- Select React as the JavaScript framework
3. This will scaffold all the necessary files and setup React in your project.
4. Import React and ReactDOM in your web part file:
```js
import * as React from 'react';
import * as ReactDom from 'react-dom';
```
5. Create a simple React component: