Open the Instagram app
Go to the post where you want to comment
Tap the comment field
Check whether the GIF button or sticker option is available in your version of Instagram
Tap the GIF button if shown
Search for a GIF using keywords
Select the GIF you want to post
Tap send or post
If no GIF option appears, update Instagram to the latest version
If GIFs are still unavailable, use a supported keyboard or third-party app if allowed on your device
Make sure your account and the post allow comments