To download Instagram on your iPhone, follow these simple steps:
1. Open the App Store on your iPhone.
2. Tap on the search icon in the bottom right corner of the screen.
3. Type "Instagram" in the search bar and tap on the search button.
4. Tap on the Instagram app in the search results.
5. Tap on the "Get" button next to the app icon.
6. If prompted, enter your Apple ID password or use Touch ID or Face ID to authenticate the download.
7. Wait for the app to download and install on your iPhone.
8. Once the installation is complete, you can open the app and sign up or log in to your existing account to start using Instagram.