Begin by setting up a local or cloud environment where you will run your scripts. Ensure you have Node.js and MongoDB installed on your system. Node.js will be used to write the script that fetches data from the API and inserts it into MongoDB.

Identify the exchange rates API you want to use and obtain an API key if required. Familiarize yourself with the endpoint from which you will fetch the data. This typically involves a simple GET request. For example, if using a service like ExchangeRate-API, your endpoint might look like `https://api.exchangerate-api.com/v4/latest/USD`.

Create a new Node.js script to fetch data from the API. Utilize the `axios` library to make HTTP requests. First, install axios by running `npm install axios`. Then, write a function within your script to fetch the data:

```javascript
const axios = require('axios');

async function fetchExchangeRates() {
try {
const response = await axios.get('https://api.exchangerate-api.com/v4/latest/USD'); // Replace with your API URL
return response.data;
} catch (error) {
console.error('Error fetching data:', error);
return null;
}
}
```

In the same Node.js script, set up a connection to your MongoDB database. Use the `mongodb` package for this purpose. Install it via `npm install mongodb`. Then, establish a connection:

```javascript
const { MongoClient } = require('mongodb');

async function connectToMongoDB() {
const uri = 'mongodb://localhost:27017'; // Replace with your MongoDB URI
const client = new MongoClient(uri, { useNewUrlParser: true, useUnifiedTopology: true });

try {
await client.connect();
console.log('Connected to MongoDB');
return client;
} catch (error) {
console.error('MongoDB connection error:', error);
return null;
}
}
```

With both the exchange rates data and MongoDB connection ready, write a function to insert the data into a specified collection in your MongoDB database:

```javascript
async function insertDataToMongoDB(client, data) {
try {
const database = client.db('exchangeRatesDB'); // Replace with your database name
const collection = database.collection('rates'); // Replace with your collection name
const result = await collection.insertOne(data);
console.log(`Data inserted with id: ${result.insertedId}`);
} catch (error) {
console.error('Error inserting data:', error);
}
}
```

Now, you can execute the entire data transfer process in a coordinated manner. Write a main function to fetch the data, connect to MongoDB, and insert the data:

```javascript
async function main() {
const exchangeRates = await fetchExchangeRates();
if (!exchangeRates) return;

const client = await connectToMongoDB();
if (!client) return;

await insertDataToMongoDB(client, exchangeRates);

await client.close();
}

main().catch(console.error);
```

To automate this process, you can use a scheduling tool like `cron` on Unix-based systems or Task Scheduler on Windows to run your Node.js script at desired intervals. Alternatively, integrate a scheduling library like `node-cron` into your script for more control over the scheduling directly in your Node.js environment.

```javascript
const cron = require('node-cron');

cron.schedule('0 ', () => { // Runs every hour
console.log('Running data transfer script...');
main().catch(console.error);
});
```

This guide provides a straightforward approach to moving data from an exchange rates API to a MongoDB database using Node.js, without relying on third-party connectors or integrations.