If you are set your custom or uploaded profile picture and need to see on front end, you can use below function .
<?php echo get_avatar( $id_or_email, $size, $default, $alt, $args ); ?>
If you have to change your gravatar to custom profile picture you can refer below link :
http://www.wpbeginner.com/wp-tutorials/how-to-change-the-default-gravatar-on-wordpress/