Follow the following steps:
1. Login to your Instagram account from any computer.
2. Make sure your Instagram Account is Public.
2. Click on any Instagram photo you have uploaded.
3. After Clicking, photo will be open in a PopUp/ Modal window. Now See the Web URL in the browser. URL will be like this - https://www.instagram.com/p/BHZbdo1jjS3/?taken-by=shadhin_int&hl=en. In this URL "BHZbdo1jjS3" is the Feed ID.
4. See the attached image below, the red marked section after (/p/) is the Feed ID of this post/feed.
5. You can copy these Feed IDs from your Instagram account and use it in the back end of "Responsive Custom Instagram Feed" Module.