To download Instagram, simply head to the App Store on your iPhone 6, search for "Instagram", and click the "Get" button. Then, wait for the app to download and install, and you're ready to start 'gramming! You'll need to create an account or log in if you already have one.
Once you're all set up, you can start exploring the world of Instagram. You'll find a feed full of posts from accounts you follow, and you can like, comment, and share your favorite pics and vids. You can also use the Stories feature to share behind-the-scenes glimpses into your daily life.