Begin by setting up a Python environment on your local machine or server. Ensure you have Python installed, and then create a virtual environment to manage dependencies. Use the following commands:
```bash
python3 -m venv myenv
source myenv/bin/activate # On Windows, use myenv\Scripts\activate
```

Install the necessary Python libraries to interact with Coin API and MongoDB. Use the `requests` library to make HTTP requests to Coin API and `pymongo` to interact with MongoDB:
```bash
pip install requests pymongo
```

Write a Python script to fetch data from Coin API. You will need to obtain an API key from Coin API and include it in your request headers. Here’s a basic example:
```python
import requests

api_key = 'YOUR_COIN_API_KEY'
url = 'https://rest.coinapi.io/v1/exchangerate/BTC/USD'

headers = {'X-CoinAPI-Key': api_key}
response = requests.get(url, headers=headers)

if response.status_code == 200:
data = response.json()
print(data) # Verify the data structure
else:
print(f"Failed to retrieve data: {response.status_code}")
```

Ensure MongoDB is installed and running on your local machine or accessible on your network. You can download MongoDB from its official website and start the service. The default connection string for a local instance is:
```plaintext
mongodb://localhost:27017/
```

Use `pymongo` to establish a connection to your MongoDB instance. Decide on a database and collection where you want to store the retrieved data:
```python
from pymongo import MongoClient

client = MongoClient('mongodb://localhost:27017/')
db = client['coin_data'] # Create or use existing database
collection = db['exchange_rates'] # Create or use existing collection
```

After retrieving data from Coin API, insert it into the MongoDB collection. Convert the data into a dictionary format suitable for MongoDB:
```python
if response.status_code == 200:
data = response.json()
# Insert data into MongoDB
collection.insert_one(data)
print("Data inserted successfully.")
```

To keep your data up-to-date, automate the data retrieval and insertion process using a scheduling tool like `cron` (Linux/macOS) or Task Scheduler (Windows). Create a Python script that includes all the above steps and schedule it to run at your desired frequency. For example, to schedule a cron job, edit the crontab file:
```bash
crontab -e
```
Add a line to run the script every hour:
```plaintext
0 /path/to/python /path/to/your_script.py
```

This guide provides a structured approach to fetching data from Coin API and storing it in MongoDB, using Python as the intermediary without relying on third-party connectors.