Open Instagram and go to the post
Tap the comment field
Tap the sticker or GIF option if available in your keyboard or app
Search for a GIF
Select the GIF you want
Post the comment
If GIF comments are not available on your account
Update the Instagram app
Check if your keyboard app supports GIFs
Use a GIF as a story reply or DM instead
Try again later if the feature is not enabled for your region or account