Only some themes display the Bio Info / Profile Picture on the bottom of blog posts. Please check in APPEARANCE > THEME OPTIONS if this feature is available for your theme. If it doesn’t appear, that’s because it is not available for the theme you’re currently using.
You can always add the ABOUT widget to your blog’s sidebar in APPEARANCE > WIDGETS. Just bare in mind that the avatar this widget will display is your blog’s avatar, which you can upload in SETTINGS > GENERAL.