1. First things first, make sure you've got Node.js and npm (Node Package Manager) installed on your machine. If not, you can grab them from nodejs.org.
2. Create a new directory for your project and navigate into it:
   ```bash
   mkdir my-express-app
   cd my-express-app
   ```
3. Initialize a new Node.js project using npm:
   ```bash
   npm init -y
   ```
4. Install Express.js:
   ```bash
   npm install express
   ```

1. Install the Supabase client library:
   ```bash
   npm install @supabase/supabase-js
   ```

1. Head over to the Supabase website and sign up if you don't already have an account.
2. Create a new project and jot down your API URL and anon key. You'll need these to configure your Supabase client.

1. Create a new file named app.js in your project directory:
   ```bash
   touch app.js
   ```

2. Open app.js in your text editor and set up a basic Express server:

   ```javascript
   const express = require('express');
   const { createClient } = require('@supabase/supabase-js');

   const app = express();
   const port = 3000;

   const SUPABASE_URL = 'https://your-supabase-url.supabase.co';
   const SUPABASE_ANON_KEY = 'your-supabase-anon-key';

   const supabase = createClient(SUPABASE_URL, SUPABASE_ANON_KEY);

   app.use(express.json());

   app.get('/', (req, res) => {
   res.send('Hello World!');
   });

   app.listen(port, () => {
   console.log(Server running at http://localhost:${port});
   });
   ```

3. Replace https://your-supabase-url.supabase.co and your-supabase-anon-key with the actual values from your Supabase project.

1. To interact with your database, create a new route in app.js. Here's an example route to fetch data from a table named users:

   ```javascript
   app.get('/users', async (req, res) => {
   const { data, error } = await supabase
   .from('users')
   .select('*');
   if (error) {
   console.error(error);
   return res.status(500).json({ error: error.message });
   }

   res.json(data);
   });
   ```

2. To insert data into the users table, add a POST route:

   ```javascript
   app.post('/users', async (req, res) => {
   const { name, email } = req.body;
   const { data, error } = await supabase
   .from('users')
   .insert([{ name, email }]);
   if (error) {
   console.error(error);
   return res.status(500).json({ error: error.message });
   }

   res.status(201).json(data);
   });
   ```

1. Start your Express.js server:
   ```bash
   node app.js
   ```
2. Open your browser or a tool like Postman and navigate to http://localhost:3000/users to fetch users or send a POST request to http://localhost:3000/users with JSON data { "name": "John Doe", "email": "[email protected]" } to insert a new user.

Now the Supabase and Express.js integration is ready for further development!