Unfortunately, you cannot edit a comment on Instagram once it has been posted. If you need to make a correction or add more information to your comment, your best option is to delete the original comment and repost a new one with the updated content.

To delete a comment on Instagram, follow these steps:

1. Open the Instagram app and go to your profile.
2. Select the post with the comment you want to delete.
3. Find the comment you want to delete and swipe left on it.
4. Tap the trash can icon that appears.
5. Confirm that you want to delete the comment.

Once you've deleted the original comment, you can post a new one with the updated content.