To access Instagram's API, you need to be registered as a Facebook Developer and create an app.

1. Go to https://developers.facebook.com/ and log in with your Facebook account.

2. Click on "My Apps" and then "Create App."

3. Choose the app type that fits your needs (for data fetching, "Consumer" might be appropriate).

4. Fill in the required details and create the app.

Instagram's Basic Display API allows you to read basic profile information and media.

1. In your app dashboard, navigate to "Products" and add "Instagram Basic Display."

2. Fill in the required fields in the settings, such as the "Privacy Policy URL."

3. Add an Instagram Test User in the "Roles" section to test your app.

To access Instagram data, you'll need an access token.

1. Navigate to the "Basic Display" tab and scroll down to "User Token Generator."

2. Authenticate the test user you added earlier to generate a token.

Use the access token to make API calls to Instagram using a scripting language like Python.

1. Install the `requests` library if you haven't already: `pip install requests`.

2. Write a script to fetch data from Instagram:

```python

import requests

access_token = 'YOUR_ACCESS_TOKEN'

user_id = 'YOUR_USER_ID'

url = f'https://graph.instagram.com/{user_id}?fields=id,username,media_count&access_token={access_token}'

response = requests.get(url)

if response.status_code == 200:

    data = response.json()

    print(data)

else:

    print('Failed to fetch data')

```

For Google Sheets, you'll use Google Apps Script to insert data.

1. Go to Google Drive and create a new Google Sheet.

2. Click on "Extensions" > "Apps Script."

3. Rename the project to something meaningful.

In the Apps Script editor, write a script to insert data into the Google Sheet.

```javascript

function insertInstagramData(instagramData) {

  var sheet = SpreadsheetApp.getActiveSpreadsheet().getActiveSheet();

  // Assuming instagramData is an array of arrays e.g., [[username, media_count]]

  var range = sheet.getRange(sheet.getLastRow() + 1, 1, instagramData.length, instagramData[0].length);

  range.setValues(instagramData);

}

```

Now you'll need to combine the Instagram data fetching with the Google Sheets scripting.

1. Modify your Python script to send the data to Google Apps Script using Google Sheets API.

2. Alternatively, use Google Apps Script's `UrlFetchApp` to fetch data directly from Instagram and insert it into Google Sheets.

Here's an example using `UrlFetchApp` in Google Apps Script:

```javascript

function fetchInstagramData() {

  var accessToken = 'YOUR_ACCESS_TOKEN';

  var userId = 'YOUR_USER_ID';

  var url = 'https://graph.instagram.com/' + userId + '?fields=id,username,media_count&access_token=' + accessToken;

  var response = UrlFetchApp.fetch(url);

  var json = JSON.parse(response.getContentText());

  // Assuming you want to insert username and media count

  var instagramData = [[json.username, json.media_count]];

  insertInstagramData(instagramData);

}

// Don't forget to define insertInstagramData function as shown in Step 6

```

You can set a trigger to run the `fetchInstagramData` function periodically.

1. In the Apps Script editor, click on the clock icon (current project's triggers).

2. Click on "+ Add Trigger" and select the `fetchInstagramData` function.

3. Choose the type of trigger you want (e.g., Time-driven) and set the frequency.

Run your scripts and check if the data is being inserted into Google Sheets correctly. Debug any issues that arise.