We don't really know who Buster is just from this title. He could be an ordinary person whose story has been told to illustrate a particular point about having a'mal heart', whether it's about his character flaws or some sort of misfortune he has faced.
Posting a GIF on Story is easy. You basically go to the Story creation area, find the button for adding stuff like pictures or GIFs. Once you click that, choose your GIF from your files and it'll upload. Just keep in mind that sometimes there might be restrictions on the size or type of GIF that can be posted.
Well, to add a GIF to a story, first, make sure you have the GIF saved on your device or know the URL of the one you want. Then, depending on the platform you're using, like a blog or a document editor, look for the option to insert images or media. Select that and choose the GIF from your files or paste the URL. Some platforms might also have specific formatting or size adjustments you can make.