Hello,
To add the social icon for your social site, first of all add a custom CSS plugin to your site.
You can use this plugin : https://wordpress.org/plugins/so-css/
After you have added the plugin go to
Dashboard -> Appearance -> Custom CSS and add the below given CSS.
.photo_perfect_widget_social ul li a[href*="vk.com"]:before {
content: "\f189";
}
.photo_perfect_widget_social ul li a[href*="vk.com"]:hover {
background-color: #03A9F4;
}
Hope it helps.
Best regards.