How do I style my plugin?
Your widget, form, social share buttons, etc., typically come with styles that have been set by the plugin, but this doesn't mean that you can't change them!
Use your browser's developer tools to look for classes and/or ids used by the plugin. You can use those specific selectors to style individual elements. Just make sure that you make your CSS changes in your theme's style.css file, and not in the plugin's files. Keeping the changes in your theme's style.css file means you can update the plugin safely without losing your changes. Whew!
As with all plugins, reading the plugin documentation is often worth the time investment! You may find a few built-in classes that you can use to help you towards achieving the look that you are after. :)