You might see a post on Facebook that you would like to comment on. Tap the Comment icon beneath the post.
Type your comment. You can also tap the Emoji icon on the right-hand side of the text box in order to add emojis (like a heart or smiley face).
Then tap Post, and you’ll see your comment beneath the post.
Keep in mind that users can delete comments you make on their posts, and you can also delete comments that you wrote. You cannot delete comments that other users write on a post that doesn’t belong to you.